OK, let's work through this together. We're starting with 688 and we're going to multiply it by 342, which means we add 688 to itself 342 times.
Step 1: 0 + 688 = 688
Step 2: 688 + 688 = 1376
Step 3: 1376 + 688 = 2064
Step 4: 2064 + 688 = 2752
Step 5: 2752 + 688 = 3440
Step 6: 3440 + 688 = 4128
Step 7: 4128 + 688 = 4816
Step 8: 4816 + 688 = 5504
Step 9: 5504 + 688 = 6192
Step 10: 6192 + 688 = 6880
Step 11: 6880 + 688 = 7568
Step 12: 7568 + 688 = 8256
Step 13: 8256 + 688 = 8944
Step 14: 8944 + 688 = 9632
Step 15: 9632 + 688 = 10320
Step 16: 10320 + 688 = 11008
Step 17: 11008 + 688 = 11696
Step 18: 11696 + 688 = 12384
Step 19: 12384 + 688 = 13072
Step 20: 13072 + 688 = 13760
Step 21: 13760 + 688 = 14448
Step 22: 14448 + 688 = 15136
Step 23: 15136 + 688 = 15824
Step 24: 15824 + 688 = 16512
Step 25: 16512 + 688 = 17200
Step 26: 17200 + 688 = 17888
Step 27: 17888 + 688 = 18576
Step 28: 18576 + 688 = 19264
Step 29: 19264 + 688 = 19952
Step 30: 19952 + 688 = 20640
Step 31: 20640 + 688 = 21328
Step 32: 21328 + 688 = 22016
Step 33: 22016 + 688 = 22704
Step 34: 22704 + 688 = 23392
Step 35: 23392 + 688 = 24080
Step 36: 24080 + 688 = 24768
Step 37: 24768 + 688 = 25456
Step 38: 25456 + 688 = 26144
Step 39: 26144 + 688 = 26832
Step 40: 26832 + 688 = 27520
Step 41: 27520 + 688 = 28208
Step 42: 28208 + 688 = 28896
Step 43: 28896 + 688 = 29584
Step 44: 29584 + 688 = 30272
Step 45: 30272 + 688 = 30960
Step 46: 30960 + 688 = 31648
Step 47: 31648 + 688 = 32336
Step 48: 32336 + 688 = 33024
Step 49: 33024 + 688 = 33712
Step 50: 33712 + 688 = 34400
Step 51: 34400 + 688 = 35088
Step 52: 35088 + 688 = 35776
Step 53: 35776 + 688 = 36464
Step 54: 36464 + 688 = 37152
Step 55: 37152 + 688 = 37840
Step 56: 37840 + 688 = 38528
Step 57: 38528 + 688 = 39216
Step 58: 39216 + 688 = 39904
Step 59: 39904 + 688 = 40592
Step 60: 40592 + 688 = 41280
Step 61: 41280 + 688 = 41968
Step 62: 41968 + 688 = 42656
Step 63: 42656 + 688 = 43344
Step 64: 43344 + 688 = 44032
Step 65: 44032 + 688 = 44720
Step 66: 44720 + 688 = 45408
Step 67: 45408 + 688 = 46096
Step 68: 46096 + 688 = 46784
Step 69: 46784 + 688 = 47472
Step 70: 47472 + 688 = 48160
Step 71: 48160 + 688 = 48848
Step 72: 48848 + 688 = 49536
Step 73: 49536 + 688 = 50224
Step 74: 50224 + 688 = 50912
Step 75: 50912 + 688 = 51600
Step 76: 51600 + 688 = 52288
Step 77: 52288 + 688 = 52976
Step 78: 52976 + 688 = 53664
Step 79: 53664 + 688 = 54352
Step 80: 54352 + 688 = 55040
Step 81: 55040 + 688 = 55728
Step 82: 55728 + 688 = 56416
Step 83: 56416 + 688 = 57104
Step 84: 57104 + 688 = 57792
Step 85: 57792 + 688 = 58480
Step 86: 58480 + 688 = 59168
Step 87: 59168 + 688 = 59856
Step 88: 59856 + 688 = 60544
Step 89: 60544 + 688 = 61232
Step 90: 61232 + 688 = 61920
Step 91: 61920 + 688 = 62608
Step 92: 62608 + 688 = 63296
Step 93: 63296 + 688 = 63984
Step 94: 63984 + 688 = 64672
Step 95: 64672 + 688 = 65360
Step 96: 65360 + 688 = 66048
Step 97: 66048 + 688 = 66736
Step 98: 66736 + 688 = 67424
Step 99: 67424 + 688 = 68112
Step 100: 68112 + 688 = 68800
Step 101: 68800 + 688 = 69488
Step 102: 69488 + 688 = 70176
Step 103: 70176 + 688 = 70864
Step 104: 70864 + 688 = 71552
Step 105: 71552 + 688 = 72240
Step 106: 72240 + 688 = 72928
Step 107: 72928 + 688 = 73616
Step 108: 73616 + 688 = 74304
Step 109: 74304 + 688 = 74992
Step 110: 74992 + 688 = 75680
Step 111: 75680 + 688 = 76368
Step 112: 76368 + 688 = 77056
Step 113: 77056 + 688 = 77744
Step 114: 77744 + 688 = 78432
Step 115: 78432 + 688 = 79120
Step 116: 79120 + 688 = 79808
Step 117: 79808 + 688 = 80496
Step 118: 80496 + 688 = 81184
Step 119: 81184 + 688 = 81872
Step 120: 81872 + 688 = 82560
Step 121: 82560 + 688 = 83248
Step 122: 83248 + 688 = 83936
Step 123: 83936 + 688 = 84624
Step 124: 84624 + 688 = 85312
Step 125: 85312 + 688 = 86000
Step 126: 86000 + 688 = 86688
Step 127: 86688 + 688 = 87376
Step 128: 87376 + 688 = 88064
Step 129: 88064 + 688 = 88752
Step 130: 88752 + 688 = 89440
Step 131: 89440 + 688 = 90128
Step 132: 90128 + 688 = 90816
Step 133: 90816 + 688 = 91504
Step 134: 91504 + 688 = 92192
Step 135: 92192 + 688 = 92880
Step 136: 92880 + 688 = 93568
Step 137: 93568 + 688 = 94256
Step 138: 94256 + 688 = 94944
Step 139: 94944 + 688 = 95632
Step 140: 95632 + 688 = 96320
Step 141: 96320 + 688 = 97008
Step 142: 97008 + 688 = 97696
Step 143: 97696 + 688 = 98384
Step 144: 98384 + 688 = 99072
Step 145: 99072 + 688 = 99760
Step 146: 99760 + 688 = 100448
Step 147: 100448 + 688 = 101136
Step 148: 101136 + 688 = 101824
Step 149: 101824 + 688 = 102512
Step 150: 102512 + 688 = 103200
Step 151: 103200 + 688 = 103888
Step 152: 103888 + 688 = 104576
Step 153: 104576 + 688 = 105264
Step 154: 105264 + 688 = 105952
Step 155: 105952 + 688 = 106640
Step 156: 106640 + 688 = 107328
Step 157: 107328 + 688 = 108016
Step 158: 108016 + 688 = 108704
Step 159: 108704 + 688 = 109392
Step 160: 109392 + 688 = 110080
Step 161: 110080 + 688 = 110768
Step 162: 110768 + 688 = 111456
Step 163: 111456 + 688 = 112144
Step 164: 112144 + 688 = 112832
Step 165: 112832 + 688 = 113520
Step 166: 113520 + 688 = 114208
Step 167: 114208 + 688 = 114896
Step 168: 114896 + 688 = 115584
Step 169: 115584 + 688 = 116272
Step 170: 116272 + 688 = 116960
Step 171: 116960 + 688 = 117648
Step 172: 117648 + 688 = 118336
Step 173: 118336 + 688 = 119024
Step 174: 119024 + 688 = 119712
Step 175: 119712 + 688 = 120400
Step 176: 120400 + 688 = 121088
Step 177: 121088 + 688 = 121776
Step 178: 121776 + 688 = 122464
Step 179: 122464 + 688 = 123152
Step 180: 123152 + 688 = 123840
Step 181: 123840 + 688 = 124528
Step 182: 124528 + 688 = 125216
Step 183: 125216 + 688 = 125904
Step 184: 125904 + 688 = 126592
Step 185: 126592 + 688 = 127280
Step 186: 127280 + 688 = 127968
Step 187: 127968 + 688 = 128656
Step 188: 128656 + 688 = 129344
Step 189: 129344 + 688 = 130032
Step 190: 130032 + 688 = 130720
Step 191: 130720 + 688 = 131408
Step 192: 131408 + 688 = 132096
Step 193: 132096 + 688 = 132784
Step 194: 132784 + 688 = 133472
Step 195: 133472 + 688 = 134160
Step 196: 134160 + 688 = 134848
Step 197: 134848 + 688 = 135536
Step 198: 135536 + 688 = 136224
Step 199: 136224 + 688 = 136912
Step 200: 136912 + 688 = 137600
Step 201: 137600 + 688 = 138288
Step 202: 138288 + 688 = 138976
Step 203: 138976 + 688 = 139664
Step 204: 139664 + 688 = 140352
Step 205: 140352 + 688 = 141040
Step 206: 141040 + 688 = 141728
Step 207: 141728 + 688 = 142416
Step 208: 142416 + 688 = 143104
Step 209: 143104 + 688 = 143792
Step 210: 143792 + 688 = 144480
Step 211: 144480 + 688 = 145168
Step 212: 145168 + 688 = 145856
Step 213: 145856 + 688 = 146544
Step 214: 146544 + 688 = 147232
Step 215: 147232 + 688 = 147920
Step 216: 147920 + 688 = 148608
Step 217: 148608 + 688 = 149296
Step 218: 149296 + 688 = 149984
Step 219: 149984 + 688 = 150672
Step 220: 150672 + 688 = 151360
Step 221: 151360 + 688 = 152048
Step 222: 152048 + 688 = 152736
Step 223: 152736 + 688 = 153424
Step 224: 153424 + 688 = 154112
Step 225: 154112 + 688 = 154800
Step 226: 154800 + 688 = 155488
Step 227: 155488 + 688 = 156176
Step 228: 156176 + 688 = 156864
Step 229: 156864 + 688 = 157552
Step 230: 157552 + 688 = 158240
Step 231: 158240 + 688 = 158928
Step 232: 158928 + 688 = 159616
Step 233: 159616 + 688 = 160304
Step 234: 160304 + 688 = 160992
Step 235: 160992 + 688 = 161680
Step 236: 161680 + 688 = 162368
Step 237: 162368 + 688 = 163056
Step 238: 163056 + 688 = 163744
Step 239: 163744 + 688 = 164432
Step 240: 164432 + 688 = 165120
Step 241: 165120 + 688 = 165808
Step 242: 165808 + 688 = 166496
Step 243: 166496 + 688 = 167184
Step 244: 167184 + 688 = 167872
Step 245: 167872 + 688 = 168560
Step 246: 168560 + 688 = 169248
Step 247: 169248 + 688 = 169936
Step 248: 169936 + 688 = 170624
Step 249: 170624 + 688 = 171312
Step 250: 171312 + 688 = 172000
Step 251: 172000 + 688 = 172688
Step 252: 172688 + 688 = 173376
Step 253: 173376 + 688 = 174064
Step 254: 174064 + 688 = 174752
Step 255: 174752 + 688 = 175440
Step 256: 175440 + 688 = 176128
Step 257: 176128 + 688 = 176816
Step 258: 176816 + 688 = 177504
Step 259: 177504 + 688 = 178192
Step 260: 178192 + 688 = 178880
Step 261: 178880 + 688 = 179568
Step 262: 179568 + 688 = 180256
Step 263: 180256 + 688 = 180944
Step 264: 180944 + 688 = 181632
Step 265: 181632 + 688 = 182320
Step 266: 182320 + 688 = 183008
Step 267: 183008 + 688 = 183696
Step 268: 183696 + 688 = 184384
Step 269: 184384 + 688 = 185072
Step 270: 185072 + 688 = 185760
Step 271: 185760 + 688 = 186448
Step 272: 186448 + 688 = 187136
Step 273: 187136 + 688 = 187824
Step 274: 187824 + 688 = 188512
Step 275: 188512 + 688 = 189200
Step 276: 189200 + 688 = 189888
Step 277: 189888 + 688 = 190576
Step 278: 190576 + 688 = 191264
Step 279: 191264 + 688 = 191952
Step 280: 191952 + 688 = 192640
Step 281: 192640 + 688 = 193328
Step 282: 193328 + 688 = 194016
Step 283: 194016 + 688 = 194704
Step 284: 194704 + 688 = 195392
Step 285: 195392 + 688 = 196080
Step 286: 196080 + 688 = 196768
Step 287: 196768 + 688 = 197456
Step 288: 197456 + 688 = 198144
Step 289: 198144 + 688 = 198832
Step 290: 198832 + 688 = 199520
Step 291: 199520 + 688 = 200208
Step 292: 200208 + 688 = 200896
Step 293: 200896 + 688 = 201584
Step 294: 201584 + 688 = 202272
Step 295: 202272 + 688 = 202960
Step 296: 202960 + 688 = 203648
Step 297: 203648 + 688 = 204336
Step 298: 204336 + 688 = 205024
Step 299: 205024 + 688 = 205712
Step 300: 205712 + 688 = 206400
Step 301: 206400 + 688 = 207088
Step 302: 207088 + 688 = 207776
Step 303: 207776 + 688 = 208464
Step 304: 208464 + 688 = 209152
Step 305: 209152 + 688 = 209840
Step 306: 209840 + 688 = 210528
Step 307: 210528 + 688 = 211216
Step 308: 211216 + 688 = 211904
Step 309: 211904 + 688 = 212592
Step 310: 212592 + 688 = 213280
Step 311: 213280 + 688 = 213968
Step 312: 213968 + 688 = 214656
Step 313: 214656 + 688 = 215344
Step 314: 215344 + 688 = 216032
Step 315: 216032 + 688 = 216720
Step 316: 216720 + 688 = 217408
Step 317: 217408 + 688 = 218096
Step 318: 218096 + 688 = 218784
Step 319: 218784 + 688 = 219472
Step 320: 219472 + 688 = 220160
Step 321: 220160 + 688 = 220848
Step 322: 220848 + 688 = 221536
Step 323: 221536 + 688 = 222224
Step 324: 222224 + 688 = 222912
Step 325: 222912 + 688 = 223600
Step 326: 223600 + 688 = 224288
Step 327: 224288 + 688 = 224976
Step 328: 224976 + 688 = 225664
Step 329: 225664 + 688 = 226352
Step 330: 226352 + 688 = 227040
Step 331: 227040 + 688 = 227728
Step 332: 227728 + 688 = 228416
Step 333: 228416 + 688 = 229104
Step 334: 229104 + 688 = 229792
Step 335: 229792 + 688 = 230480
Step 336: 230480 + 688 = 231168
Step 337: 231168 + 688 = 231856
Step 338: 231856 + 688 = 232544
Step 339: 232544 + 688 = 233232
Step 340: 233232 + 688 = 233920
Step 341: 233920 + 688 = 234608
Step 342: 234608 + 688 = 235296

So, 688*342 = 235296