OK, let's work through this together. We're starting with 502 and we're going to multiply it by 344, which means we add 502 to itself 344 times.
Step 1: 0 + 502 = 502
Step 2: 502 + 502 = 1004
Step 3: 1004 + 502 = 1506
Step 4: 1506 + 502 = 2008
Step 5: 2008 + 502 = 2510
Step 6: 2510 + 502 = 3012
Step 7: 3012 + 502 = 3514
Step 8: 3514 + 502 = 4016
Step 9: 4016 + 502 = 4518
Step 10: 4518 + 502 = 5020
Step 11: 5020 + 502 = 5522
Step 12: 5522 + 502 = 6024
Step 13: 6024 + 502 = 6526
Step 14: 6526 + 502 = 7028
Step 15: 7028 + 502 = 7530
Step 16: 7530 + 502 = 8032
Step 17: 8032 + 502 = 8534
Step 18: 8534 + 502 = 9036
Step 19: 9036 + 502 = 9538
Step 20: 9538 + 502 = 10040
Step 21: 10040 + 502 = 10542
Step 22: 10542 + 502 = 11044
Step 23: 11044 + 502 = 11546
Step 24: 11546 + 502 = 12048
Step 25: 12048 + 502 = 12550
Step 26: 12550 + 502 = 13052
Step 27: 13052 + 502 = 13554
Step 28: 13554 + 502 = 14056
Step 29: 14056 + 502 = 14558
Step 30: 14558 + 502 = 15060
Step 31: 15060 + 502 = 15562
Step 32: 15562 + 502 = 16064
Step 33: 16064 + 502 = 16566
Step 34: 16566 + 502 = 17068
Step 35: 17068 + 502 = 17570
Step 36: 17570 + 502 = 18072
Step 37: 18072 + 502 = 18574
Step 38: 18574 + 502 = 19076
Step 39: 19076 + 502 = 19578
Step 40: 19578 + 502 = 20080
Step 41: 20080 + 502 = 20582
Step 42: 20582 + 502 = 21084
Step 43: 21084 + 502 = 21586
Step 44: 21586 + 502 = 22088
Step 45: 22088 + 502 = 22590
Step 46: 22590 + 502 = 23092
Step 47: 23092 + 502 = 23594
Step 48: 23594 + 502 = 24096
Step 49: 24096 + 502 = 24598
Step 50: 24598 + 502 = 25100
Step 51: 25100 + 502 = 25602
Step 52: 25602 + 502 = 26104
Step 53: 26104 + 502 = 26606
Step 54: 26606 + 502 = 27108
Step 55: 27108 + 502 = 27610
Step 56: 27610 + 502 = 28112
Step 57: 28112 + 502 = 28614
Step 58: 28614 + 502 = 29116
Step 59: 29116 + 502 = 29618
Step 60: 29618 + 502 = 30120
Step 61: 30120 + 502 = 30622
Step 62: 30622 + 502 = 31124
Step 63: 31124 + 502 = 31626
Step 64: 31626 + 502 = 32128
Step 65: 32128 + 502 = 32630
Step 66: 32630 + 502 = 33132
Step 67: 33132 + 502 = 33634
Step 68: 33634 + 502 = 34136
Step 69: 34136 + 502 = 34638
Step 70: 34638 + 502 = 35140
Step 71: 35140 + 502 = 35642
Step 72: 35642 + 502 = 36144
Step 73: 36144 + 502 = 36646
Step 74: 36646 + 502 = 37148
Step 75: 37148 + 502 = 37650
Step 76: 37650 + 502 = 38152
Step 77: 38152 + 502 = 38654
Step 78: 38654 + 502 = 39156
Step 79: 39156 + 502 = 39658
Step 80: 39658 + 502 = 40160
Step 81: 40160 + 502 = 40662
Step 82: 40662 + 502 = 41164
Step 83: 41164 + 502 = 41666
Step 84: 41666 + 502 = 42168
Step 85: 42168 + 502 = 42670
Step 86: 42670 + 502 = 43172
Step 87: 43172 + 502 = 43674
Step 88: 43674 + 502 = 44176
Step 89: 44176 + 502 = 44678
Step 90: 44678 + 502 = 45180
Step 91: 45180 + 502 = 45682
Step 92: 45682 + 502 = 46184
Step 93: 46184 + 502 = 46686
Step 94: 46686 + 502 = 47188
Step 95: 47188 + 502 = 47690
Step 96: 47690 + 502 = 48192
Step 97: 48192 + 502 = 48694
Step 98: 48694 + 502 = 49196
Step 99: 49196 + 502 = 49698
Step 100: 49698 + 502 = 50200
Step 101: 50200 + 502 = 50702
Step 102: 50702 + 502 = 51204
Step 103: 51204 + 502 = 51706
Step 104: 51706 + 502 = 52208
Step 105: 52208 + 502 = 52710
Step 106: 52710 + 502 = 53212
Step 107: 53212 + 502 = 53714
Step 108: 53714 + 502 = 54216
Step 109: 54216 + 502 = 54718
Step 110: 54718 + 502 = 55220
Step 111: 55220 + 502 = 55722
Step 112: 55722 + 502 = 56224
Step 113: 56224 + 502 = 56726
Step 114: 56726 + 502 = 57228
Step 115: 57228 + 502 = 57730
Step 116: 57730 + 502 = 58232
Step 117: 58232 + 502 = 58734
Step 118: 58734 + 502 = 59236
Step 119: 59236 + 502 = 59738
Step 120: 59738 + 502 = 60240
Step 121: 60240 + 502 = 60742
Step 122: 60742 + 502 = 61244
Step 123: 61244 + 502 = 61746
Step 124: 61746 + 502 = 62248
Step 125: 62248 + 502 = 62750
Step 126: 62750 + 502 = 63252
Step 127: 63252 + 502 = 63754
Step 128: 63754 + 502 = 64256
Step 129: 64256 + 502 = 64758
Step 130: 64758 + 502 = 65260
Step 131: 65260 + 502 = 65762
Step 132: 65762 + 502 = 66264
Step 133: 66264 + 502 = 66766
Step 134: 66766 + 502 = 67268
Step 135: 67268 + 502 = 67770
Step 136: 67770 + 502 = 68272
Step 137: 68272 + 502 = 68774
Step 138: 68774 + 502 = 69276
Step 139: 69276 + 502 = 69778
Step 140: 69778 + 502 = 70280
Step 141: 70280 + 502 = 70782
Step 142: 70782 + 502 = 71284
Step 143: 71284 + 502 = 71786
Step 144: 71786 + 502 = 72288
Step 145: 72288 + 502 = 72790
Step 146: 72790 + 502 = 73292
Step 147: 73292 + 502 = 73794
Step 148: 73794 + 502 = 74296
Step 149: 74296 + 502 = 74798
Step 150: 74798 + 502 = 75300
Step 151: 75300 + 502 = 75802
Step 152: 75802 + 502 = 76304
Step 153: 76304 + 502 = 76806
Step 154: 76806 + 502 = 77308
Step 155: 77308 + 502 = 77810
Step 156: 77810 + 502 = 78312
Step 157: 78312 + 502 = 78814
Step 158: 78814 + 502 = 79316
Step 159: 79316 + 502 = 79818
Step 160: 79818 + 502 = 80320
Step 161: 80320 + 502 = 80822
Step 162: 80822 + 502 = 81324
Step 163: 81324 + 502 = 81826
Step 164: 81826 + 502 = 82328
Step 165: 82328 + 502 = 82830
Step 166: 82830 + 502 = 83332
Step 167: 83332 + 502 = 83834
Step 168: 83834 + 502 = 84336
Step 169: 84336 + 502 = 84838
Step 170: 84838 + 502 = 85340
Step 171: 85340 + 502 = 85842
Step 172: 85842 + 502 = 86344
Step 173: 86344 + 502 = 86846
Step 174: 86846 + 502 = 87348
Step 175: 87348 + 502 = 87850
Step 176: 87850 + 502 = 88352
Step 177: 88352 + 502 = 88854
Step 178: 88854 + 502 = 89356
Step 179: 89356 + 502 = 89858
Step 180: 89858 + 502 = 90360
Step 181: 90360 + 502 = 90862
Step 182: 90862 + 502 = 91364
Step 183: 91364 + 502 = 91866
Step 184: 91866 + 502 = 92368
Step 185: 92368 + 502 = 92870
Step 186: 92870 + 502 = 93372
Step 187: 93372 + 502 = 93874
Step 188: 93874 + 502 = 94376
Step 189: 94376 + 502 = 94878
Step 190: 94878 + 502 = 95380
Step 191: 95380 + 502 = 95882
Step 192: 95882 + 502 = 96384
Step 193: 96384 + 502 = 96886
Step 194: 96886 + 502 = 97388
Step 195: 97388 + 502 = 97890
Step 196: 97890 + 502 = 98392
Step 197: 98392 + 502 = 98894
Step 198: 98894 + 502 = 99396
Step 199: 99396 + 502 = 99898
Step 200: 99898 + 502 = 100400
Step 201: 100400 + 502 = 100902
Step 202: 100902 + 502 = 101404
Step 203: 101404 + 502 = 101906
Step 204: 101906 + 502 = 102408
Step 205: 102408 + 502 = 102910
Step 206: 102910 + 502 = 103412
Step 207: 103412 + 502 = 103914
Step 208: 103914 + 502 = 104416
Step 209: 104416 + 502 = 104918
Step 210: 104918 + 502 = 105420
Step 211: 105420 + 502 = 105922
Step 212: 105922 + 502 = 106424
Step 213: 106424 + 502 = 106926
Step 214: 106926 + 502 = 107428
Step 215: 107428 + 502 = 107930
Step 216: 107930 + 502 = 108432
Step 217: 108432 + 502 = 108934
Step 218: 108934 + 502 = 109436
Step 219: 109436 + 502 = 109938
Step 220: 109938 + 502 = 110440
Step 221: 110440 + 502 = 110942
Step 222: 110942 + 502 = 111444
Step 223: 111444 + 502 = 111946
Step 224: 111946 + 502 = 112448
Step 225: 112448 + 502 = 112950
Step 226: 112950 + 502 = 113452
Step 227: 113452 + 502 = 113954
Step 228: 113954 + 502 = 114456
Step 229: 114456 + 502 = 114958
Step 230: 114958 + 502 = 115460
Step 231: 115460 + 502 = 115962
Step 232: 115962 + 502 = 116464
Step 233: 116464 + 502 = 116966
Step 234: 116966 + 502 = 117468
Step 235: 117468 + 502 = 117970
Step 236: 117970 + 502 = 118472
Step 237: 118472 + 502 = 118974
Step 238: 118974 + 502 = 119476
Step 239: 119476 + 502 = 119978
Step 240: 119978 + 502 = 120480
Step 241: 120480 + 502 = 120982
Step 242: 120982 + 502 = 121484
Step 243: 121484 + 502 = 121986
Step 244: 121986 + 502 = 122488
Step 245: 122488 + 502 = 122990
Step 246: 122990 + 502 = 123492
Step 247: 123492 + 502 = 123994
Step 248: 123994 + 502 = 124496
Step 249: 124496 + 502 = 124998
Step 250: 124998 + 502 = 125500
Step 251: 125500 + 502 = 126002
Step 252: 126002 + 502 = 126504
Step 253: 126504 + 502 = 127006
Step 254: 127006 + 502 = 127508
Step 255: 127508 + 502 = 128010
Step 256: 128010 + 502 = 128512
Step 257: 128512 + 502 = 129014
Step 258: 129014 + 502 = 129516
Step 259: 129516 + 502 = 130018
Step 260: 130018 + 502 = 130520
Step 261: 130520 + 502 = 131022
Step 262: 131022 + 502 = 131524
Step 263: 131524 + 502 = 132026
Step 264: 132026 + 502 = 132528
Step 265: 132528 + 502 = 133030
Step 266: 133030 + 502 = 133532
Step 267: 133532 + 502 = 134034
Step 268: 134034 + 502 = 134536
Step 269: 134536 + 502 = 135038
Step 270: 135038 + 502 = 135540
Step 271: 135540 + 502 = 136042
Step 272: 136042 + 502 = 136544
Step 273: 136544 + 502 = 137046
Step 274: 137046 + 502 = 137548
Step 275: 137548 + 502 = 138050
Step 276: 138050 + 502 = 138552
Step 277: 138552 + 502 = 139054
Step 278: 139054 + 502 = 139556
Step 279: 139556 + 502 = 140058
Step 280: 140058 + 502 = 140560
Step 281: 140560 + 502 = 141062
Step 282: 141062 + 502 = 141564
Step 283: 141564 + 502 = 142066
Step 284: 142066 + 502 = 142568
Step 285: 142568 + 502 = 143070
Step 286: 143070 + 502 = 143572
Step 287: 143572 + 502 = 144074
Step 288: 144074 + 502 = 144576
Step 289: 144576 + 502 = 145078
Step 290: 145078 + 502 = 145580
Step 291: 145580 + 502 = 146082
Step 292: 146082 + 502 = 146584
Step 293: 146584 + 502 = 147086
Step 294: 147086 + 502 = 147588
Step 295: 147588 + 502 = 148090
Step 296: 148090 + 502 = 148592
Step 297: 148592 + 502 = 149094
Step 298: 149094 + 502 = 149596
Step 299: 149596 + 502 = 150098
Step 300: 150098 + 502 = 150600
Step 301: 150600 + 502 = 151102
Step 302: 151102 + 502 = 151604
Step 303: 151604 + 502 = 152106
Step 304: 152106 + 502 = 152608
Step 305: 152608 + 502 = 153110
Step 306: 153110 + 502 = 153612
Step 307: 153612 + 502 = 154114
Step 308: 154114 + 502 = 154616
Step 309: 154616 + 502 = 155118
Step 310: 155118 + 502 = 155620
Step 311: 155620 + 502 = 156122
Step 312: 156122 + 502 = 156624
Step 313: 156624 + 502 = 157126
Step 314: 157126 + 502 = 157628
Step 315: 157628 + 502 = 158130
Step 316: 158130 + 502 = 158632
Step 317: 158632 + 502 = 159134
Step 318: 159134 + 502 = 159636
Step 319: 159636 + 502 = 160138
Step 320: 160138 + 502 = 160640
Step 321: 160640 + 502 = 161142
Step 322: 161142 + 502 = 161644
Step 323: 161644 + 502 = 162146
Step 324: 162146 + 502 = 162648
Step 325: 162648 + 502 = 163150
Step 326: 163150 + 502 = 163652
Step 327: 163652 + 502 = 164154
Step 328: 164154 + 502 = 164656
Step 329: 164656 + 502 = 165158
Step 330: 165158 + 502 = 165660
Step 331: 165660 + 502 = 166162
Step 332: 166162 + 502 = 166664
Step 333: 166664 + 502 = 167166
Step 334: 167166 + 502 = 167668
Step 335: 167668 + 502 = 168170
Step 336: 168170 + 502 = 168672
Step 337: 168672 + 502 = 169174
Step 338: 169174 + 502 = 169676
Step 339: 169676 + 502 = 170178
Step 340: 170178 + 502 = 170680
Step 341: 170680 + 502 = 171182
Step 342: 171182 + 502 = 171684
Step 343: 171684 + 502 = 172186
Step 344: 172186 + 502 = 172688

So, 502*344 = 172688