Alright, let's solve this math problem step by step. First, we have the number 129. Next, we see the multiplication sign, which means we need to multiply something. And what are we multiplying it by? We multiply it by 400. So, we're going to take the number 129 and add it to itself 400 times.
Step 1: 0 + 129 = 129
Step 2: 129 + 129 = 258
Step 3: 258 + 129 = 387
Step 4: 387 + 129 = 516
Step 5: 516 + 129 = 645
Step 6: 645 + 129 = 774
Step 7: 774 + 129 = 903
Step 8: 903 + 129 = 1032
Step 9: 1032 + 129 = 1161
Step 10: 1161 + 129 = 1290
Step 11: 1290 + 129 = 1419
Step 12: 1419 + 129 = 1548
Step 13: 1548 + 129 = 1677
Step 14: 1677 + 129 = 1806
Step 15: 1806 + 129 = 1935
Step 16: 1935 + 129 = 2064
Step 17: 2064 + 129 = 2193
Step 18: 2193 + 129 = 2322
Step 19: 2322 + 129 = 2451
Step 20: 2451 + 129 = 2580
Step 21: 2580 + 129 = 2709
Step 22: 2709 + 129 = 2838
Step 23: 2838 + 129 = 2967
Step 24: 2967 + 129 = 3096
Step 25: 3096 + 129 = 3225
Step 26: 3225 + 129 = 3354
Step 27: 3354 + 129 = 3483
Step 28: 3483 + 129 = 3612
Step 29: 3612 + 129 = 3741
Step 30: 3741 + 129 = 3870
Step 31: 3870 + 129 = 3999
Step 32: 3999 + 129 = 4128
Step 33: 4128 + 129 = 4257
Step 34: 4257 + 129 = 4386
Step 35: 4386 + 129 = 4515
Step 36: 4515 + 129 = 4644
Step 37: 4644 + 129 = 4773
Step 38: 4773 + 129 = 4902
Step 39: 4902 + 129 = 5031
Step 40: 5031 + 129 = 5160
Step 41: 5160 + 129 = 5289
Step 42: 5289 + 129 = 5418
Step 43: 5418 + 129 = 5547
Step 44: 5547 + 129 = 5676
Step 45: 5676 + 129 = 5805
Step 46: 5805 + 129 = 5934
Step 47: 5934 + 129 = 6063
Step 48: 6063 + 129 = 6192
Step 49: 6192 + 129 = 6321
Step 50: 6321 + 129 = 6450
Step 51: 6450 + 129 = 6579
Step 52: 6579 + 129 = 6708
Step 53: 6708 + 129 = 6837
Step 54: 6837 + 129 = 6966
Step 55: 6966 + 129 = 7095
Step 56: 7095 + 129 = 7224
Step 57: 7224 + 129 = 7353
Step 58: 7353 + 129 = 7482
Step 59: 7482 + 129 = 7611
Step 60: 7611 + 129 = 7740
Step 61: 7740 + 129 = 7869
Step 62: 7869 + 129 = 7998
Step 63: 7998 + 129 = 8127
Step 64: 8127 + 129 = 8256
Step 65: 8256 + 129 = 8385
Step 66: 8385 + 129 = 8514
Step 67: 8514 + 129 = 8643
Step 68: 8643 + 129 = 8772
Step 69: 8772 + 129 = 8901
Step 70: 8901 + 129 = 9030
Step 71: 9030 + 129 = 9159
Step 72: 9159 + 129 = 9288
Step 73: 9288 + 129 = 9417
Step 74: 9417 + 129 = 9546
Step 75: 9546 + 129 = 9675
Step 76: 9675 + 129 = 9804
Step 77: 9804 + 129 = 9933
Step 78: 9933 + 129 = 10062
Step 79: 10062 + 129 = 10191
Step 80: 10191 + 129 = 10320
Step 81: 10320 + 129 = 10449
Step 82: 10449 + 129 = 10578
Step 83: 10578 + 129 = 10707
Step 84: 10707 + 129 = 10836
Step 85: 10836 + 129 = 10965
Step 86: 10965 + 129 = 11094
Step 87: 11094 + 129 = 11223
Step 88: 11223 + 129 = 11352
Step 89: 11352 + 129 = 11481
Step 90: 11481 + 129 = 11610
Step 91: 11610 + 129 = 11739
Step 92: 11739 + 129 = 11868
Step 93: 11868 + 129 = 11997
Step 94: 11997 + 129 = 12126
Step 95: 12126 + 129 = 12255
Step 96: 12255 + 129 = 12384
Step 97: 12384 + 129 = 12513
Step 98: 12513 + 129 = 12642
Step 99: 12642 + 129 = 12771
Step 100: 12771 + 129 = 12900
Step 101: 12900 + 129 = 13029
Step 102: 13029 + 129 = 13158
Step 103: 13158 + 129 = 13287
Step 104: 13287 + 129 = 13416
Step 105: 13416 + 129 = 13545
Step 106: 13545 + 129 = 13674
Step 107: 13674 + 129 = 13803
Step 108: 13803 + 129 = 13932
Step 109: 13932 + 129 = 14061
Step 110: 14061 + 129 = 14190
Step 111: 14190 + 129 = 14319
Step 112: 14319 + 129 = 14448
Step 113: 14448 + 129 = 14577
Step 114: 14577 + 129 = 14706
Step 115: 14706 + 129 = 14835
Step 116: 14835 + 129 = 14964
Step 117: 14964 + 129 = 15093
Step 118: 15093 + 129 = 15222
Step 119: 15222 + 129 = 15351
Step 120: 15351 + 129 = 15480
Step 121: 15480 + 129 = 15609
Step 122: 15609 + 129 = 15738
Step 123: 15738 + 129 = 15867
Step 124: 15867 + 129 = 15996
Step 125: 15996 + 129 = 16125
Step 126: 16125 + 129 = 16254
Step 127: 16254 + 129 = 16383
Step 128: 16383 + 129 = 16512
Step 129: 16512 + 129 = 16641
Step 130: 16641 + 129 = 16770
Step 131: 16770 + 129 = 16899
Step 132: 16899 + 129 = 17028
Step 133: 17028 + 129 = 17157
Step 134: 17157 + 129 = 17286
Step 135: 17286 + 129 = 17415
Step 136: 17415 + 129 = 17544
Step 137: 17544 + 129 = 17673
Step 138: 17673 + 129 = 17802
Step 139: 17802 + 129 = 17931
Step 140: 17931 + 129 = 18060
Step 141: 18060 + 129 = 18189
Step 142: 18189 + 129 = 18318
Step 143: 18318 + 129 = 18447
Step 144: 18447 + 129 = 18576
Step 145: 18576 + 129 = 18705
Step 146: 18705 + 129 = 18834
Step 147: 18834 + 129 = 18963
Step 148: 18963 + 129 = 19092
Step 149: 19092 + 129 = 19221
Step 150: 19221 + 129 = 19350
Step 151: 19350 + 129 = 19479
Step 152: 19479 + 129 = 19608
Step 153: 19608 + 129 = 19737
Step 154: 19737 + 129 = 19866
Step 155: 19866 + 129 = 19995
Step 156: 19995 + 129 = 20124
Step 157: 20124 + 129 = 20253
Step 158: 20253 + 129 = 20382
Step 159: 20382 + 129 = 20511
Step 160: 20511 + 129 = 20640
Step 161: 20640 + 129 = 20769
Step 162: 20769 + 129 = 20898
Step 163: 20898 + 129 = 21027
Step 164: 21027 + 129 = 21156
Step 165: 21156 + 129 = 21285
Step 166: 21285 + 129 = 21414
Step 167: 21414 + 129 = 21543
Step 168: 21543 + 129 = 21672
Step 169: 21672 + 129 = 21801
Step 170: 21801 + 129 = 21930
Step 171: 21930 + 129 = 22059
Step 172: 22059 + 129 = 22188
Step 173: 22188 + 129 = 22317
Step 174: 22317 + 129 = 22446
Step 175: 22446 + 129 = 22575
Step 176: 22575 + 129 = 22704
Step 177: 22704 + 129 = 22833
Step 178: 22833 + 129 = 22962
Step 179: 22962 + 129 = 23091
Step 180: 23091 + 129 = 23220
Step 181: 23220 + 129 = 23349
Step 182: 23349 + 129 = 23478
Step 183: 23478 + 129 = 23607
Step 184: 23607 + 129 = 23736
Step 185: 23736 + 129 = 23865
Step 186: 23865 + 129 = 23994
Step 187: 23994 + 129 = 24123
Step 188: 24123 + 129 = 24252
Step 189: 24252 + 129 = 24381
Step 190: 24381 + 129 = 24510
Step 191: 24510 + 129 = 24639
Step 192: 24639 + 129 = 24768
Step 193: 24768 + 129 = 24897
Step 194: 24897 + 129 = 25026
Step 195: 25026 + 129 = 25155
Step 196: 25155 + 129 = 25284
Step 197: 25284 + 129 = 25413
Step 198: 25413 + 129 = 25542
Step 199: 25542 + 129 = 25671
Step 200: 25671 + 129 = 25800
Step 201: 25800 + 129 = 25929
Step 202: 25929 + 129 = 26058
Step 203: 26058 + 129 = 26187
Step 204: 26187 + 129 = 26316
Step 205: 26316 + 129 = 26445
Step 206: 26445 + 129 = 26574
Step 207: 26574 + 129 = 26703
Step 208: 26703 + 129 = 26832
Step 209: 26832 + 129 = 26961
Step 210: 26961 + 129 = 27090
Step 211: 27090 + 129 = 27219
Step 212: 27219 + 129 = 27348
Step 213: 27348 + 129 = 27477
Step 214: 27477 + 129 = 27606
Step 215: 27606 + 129 = 27735
Step 216: 27735 + 129 = 27864
Step 217: 27864 + 129 = 27993
Step 218: 27993 + 129 = 28122
Step 219: 28122 + 129 = 28251
Step 220: 28251 + 129 = 28380
Step 221: 28380 + 129 = 28509
Step 222: 28509 + 129 = 28638
Step 223: 28638 + 129 = 28767
Step 224: 28767 + 129 = 28896
Step 225: 28896 + 129 = 29025
Step 226: 29025 + 129 = 29154
Step 227: 29154 + 129 = 29283
Step 228: 29283 + 129 = 29412
Step 229: 29412 + 129 = 29541
Step 230: 29541 + 129 = 29670
Step 231: 29670 + 129 = 29799
Step 232: 29799 + 129 = 29928
Step 233: 29928 + 129 = 30057
Step 234: 30057 + 129 = 30186
Step 235: 30186 + 129 = 30315
Step 236: 30315 + 129 = 30444
Step 237: 30444 + 129 = 30573
Step 238: 30573 + 129 = 30702
Step 239: 30702 + 129 = 30831
Step 240: 30831 + 129 = 30960
Step 241: 30960 + 129 = 31089
Step 242: 31089 + 129 = 31218
Step 243: 31218 + 129 = 31347
Step 244: 31347 + 129 = 31476
Step 245: 31476 + 129 = 31605
Step 246: 31605 + 129 = 31734
Step 247: 31734 + 129 = 31863
Step 248: 31863 + 129 = 31992
Step 249: 31992 + 129 = 32121
Step 250: 32121 + 129 = 32250
Step 251: 32250 + 129 = 32379
Step 252: 32379 + 129 = 32508
Step 253: 32508 + 129 = 32637
Step 254: 32637 + 129 = 32766
Step 255: 32766 + 129 = 32895
Step 256: 32895 + 129 = 33024
Step 257: 33024 + 129 = 33153
Step 258: 33153 + 129 = 33282
Step 259: 33282 + 129 = 33411
Step 260: 33411 + 129 = 33540
Step 261: 33540 + 129 = 33669
Step 262: 33669 + 129 = 33798
Step 263: 33798 + 129 = 33927
Step 264: 33927 + 129 = 34056
Step 265: 34056 + 129 = 34185
Step 266: 34185 + 129 = 34314
Step 267: 34314 + 129 = 34443
Step 268: 34443 + 129 = 34572
Step 269: 34572 + 129 = 34701
Step 270: 34701 + 129 = 34830
Step 271: 34830 + 129 = 34959
Step 272: 34959 + 129 = 35088
Step 273: 35088 + 129 = 35217
Step 274: 35217 + 129 = 35346
Step 275: 35346 + 129 = 35475
Step 276: 35475 + 129 = 35604
Step 277: 35604 + 129 = 35733
Step 278: 35733 + 129 = 35862
Step 279: 35862 + 129 = 35991
Step 280: 35991 + 129 = 36120
Step 281: 36120 + 129 = 36249
Step 282: 36249 + 129 = 36378
Step 283: 36378 + 129 = 36507
Step 284: 36507 + 129 = 36636
Step 285: 36636 + 129 = 36765
Step 286: 36765 + 129 = 36894
Step 287: 36894 + 129 = 37023
Step 288: 37023 + 129 = 37152
Step 289: 37152 + 129 = 37281
Step 290: 37281 + 129 = 37410
Step 291: 37410 + 129 = 37539
Step 292: 37539 + 129 = 37668
Step 293: 37668 + 129 = 37797
Step 294: 37797 + 129 = 37926
Step 295: 37926 + 129 = 38055
Step 296: 38055 + 129 = 38184
Step 297: 38184 + 129 = 38313
Step 298: 38313 + 129 = 38442
Step 299: 38442 + 129 = 38571
Step 300: 38571 + 129 = 38700
Step 301: 38700 + 129 = 38829
Step 302: 38829 + 129 = 38958
Step 303: 38958 + 129 = 39087
Step 304: 39087 + 129 = 39216
Step 305: 39216 + 129 = 39345
Step 306: 39345 + 129 = 39474
Step 307: 39474 + 129 = 39603
Step 308: 39603 + 129 = 39732
Step 309: 39732 + 129 = 39861
Step 310: 39861 + 129 = 39990
Step 311: 39990 + 129 = 40119
Step 312: 40119 + 129 = 40248
Step 313: 40248 + 129 = 40377
Step 314: 40377 + 129 = 40506
Step 315: 40506 + 129 = 40635
Step 316: 40635 + 129 = 40764
Step 317: 40764 + 129 = 40893
Step 318: 40893 + 129 = 41022
Step 319: 41022 + 129 = 41151
Step 320: 41151 + 129 = 41280
Step 321: 41280 + 129 = 41409
Step 322: 41409 + 129 = 41538
Step 323: 41538 + 129 = 41667
Step 324: 41667 + 129 = 41796
Step 325: 41796 + 129 = 41925
Step 326: 41925 + 129 = 42054
Step 327: 42054 + 129 = 42183
Step 328: 42183 + 129 = 42312
Step 329: 42312 + 129 = 42441
Step 330: 42441 + 129 = 42570
Step 331: 42570 + 129 = 42699
Step 332: 42699 + 129 = 42828
Step 333: 42828 + 129 = 42957
Step 334: 42957 + 129 = 43086
Step 335: 43086 + 129 = 43215
Step 336: 43215 + 129 = 43344
Step 337: 43344 + 129 = 43473
Step 338: 43473 + 129 = 43602
Step 339: 43602 + 129 = 43731
Step 340: 43731 + 129 = 43860
Step 341: 43860 + 129 = 43989
Step 342: 43989 + 129 = 44118
Step 343: 44118 + 129 = 44247
Step 344: 44247 + 129 = 44376
Step 345: 44376 + 129 = 44505
Step 346: 44505 + 129 = 44634
Step 347: 44634 + 129 = 44763
Step 348: 44763 + 129 = 44892
Step 349: 44892 + 129 = 45021
Step 350: 45021 + 129 = 45150
Step 351: 45150 + 129 = 45279
Step 352: 45279 + 129 = 45408
Step 353: 45408 + 129 = 45537
Step 354: 45537 + 129 = 45666
Step 355: 45666 + 129 = 45795
Step 356: 45795 + 129 = 45924
Step 357: 45924 + 129 = 46053
Step 358: 46053 + 129 = 46182
Step 359: 46182 + 129 = 46311
Step 360: 46311 + 129 = 46440
Step 361: 46440 + 129 = 46569
Step 362: 46569 + 129 = 46698
Step 363: 46698 + 129 = 46827
Step 364: 46827 + 129 = 46956
Step 365: 46956 + 129 = 47085
Step 366: 47085 + 129 = 47214
Step 367: 47214 + 129 = 47343
Step 368: 47343 + 129 = 47472
Step 369: 47472 + 129 = 47601
Step 370: 47601 + 129 = 47730
Step 371: 47730 + 129 = 47859
Step 372: 47859 + 129 = 47988
Step 373: 47988 + 129 = 48117
Step 374: 48117 + 129 = 48246
Step 375: 48246 + 129 = 48375
Step 376: 48375 + 129 = 48504
Step 377: 48504 + 129 = 48633
Step 378: 48633 + 129 = 48762
Step 379: 48762 + 129 = 48891
Step 380: 48891 + 129 = 49020
Step 381: 49020 + 129 = 49149
Step 382: 49149 + 129 = 49278
Step 383: 49278 + 129 = 49407
Step 384: 49407 + 129 = 49536
Step 385: 49536 + 129 = 49665
Step 386: 49665 + 129 = 49794
Step 387: 49794 + 129 = 49923
Step 388: 49923 + 129 = 50052
Step 389: 50052 + 129 = 50181
Step 390: 50181 + 129 = 50310
Step 391: 50310 + 129 = 50439
Step 392: 50439 + 129 = 50568
Step 393: 50568 + 129 = 50697
Step 394: 50697 + 129 = 50826
Step 395: 50826 + 129 = 50955
Step 396: 50955 + 129 = 51084
Step 397: 51084 + 129 = 51213
Step 398: 51213 + 129 = 51342
Step 399: 51342 + 129 = 51471
Step 400: 51471 + 129 = 51600

So, 129*400 = 51600