Let's roll up our sleeves and solve this. We have 187 and we're going to multiply it by 129, essentially adding 187 to itself 129 times.
Step 1: 0 + 187 = 187
Step 2: 187 + 187 = 374
Step 3: 374 + 187 = 561
Step 4: 561 + 187 = 748
Step 5: 748 + 187 = 935
Step 6: 935 + 187 = 1122
Step 7: 1122 + 187 = 1309
Step 8: 1309 + 187 = 1496
Step 9: 1496 + 187 = 1683
Step 10: 1683 + 187 = 1870
Step 11: 1870 + 187 = 2057
Step 12: 2057 + 187 = 2244
Step 13: 2244 + 187 = 2431
Step 14: 2431 + 187 = 2618
Step 15: 2618 + 187 = 2805
Step 16: 2805 + 187 = 2992
Step 17: 2992 + 187 = 3179
Step 18: 3179 + 187 = 3366
Step 19: 3366 + 187 = 3553
Step 20: 3553 + 187 = 3740
Step 21: 3740 + 187 = 3927
Step 22: 3927 + 187 = 4114
Step 23: 4114 + 187 = 4301
Step 24: 4301 + 187 = 4488
Step 25: 4488 + 187 = 4675
Step 26: 4675 + 187 = 4862
Step 27: 4862 + 187 = 5049
Step 28: 5049 + 187 = 5236
Step 29: 5236 + 187 = 5423
Step 30: 5423 + 187 = 5610
Step 31: 5610 + 187 = 5797
Step 32: 5797 + 187 = 5984
Step 33: 5984 + 187 = 6171
Step 34: 6171 + 187 = 6358
Step 35: 6358 + 187 = 6545
Step 36: 6545 + 187 = 6732
Step 37: 6732 + 187 = 6919
Step 38: 6919 + 187 = 7106
Step 39: 7106 + 187 = 7293
Step 40: 7293 + 187 = 7480
Step 41: 7480 + 187 = 7667
Step 42: 7667 + 187 = 7854
Step 43: 7854 + 187 = 8041
Step 44: 8041 + 187 = 8228
Step 45: 8228 + 187 = 8415
Step 46: 8415 + 187 = 8602
Step 47: 8602 + 187 = 8789
Step 48: 8789 + 187 = 8976
Step 49: 8976 + 187 = 9163
Step 50: 9163 + 187 = 9350
Step 51: 9350 + 187 = 9537
Step 52: 9537 + 187 = 9724
Step 53: 9724 + 187 = 9911
Step 54: 9911 + 187 = 10098
Step 55: 10098 + 187 = 10285
Step 56: 10285 + 187 = 10472
Step 57: 10472 + 187 = 10659
Step 58: 10659 + 187 = 10846
Step 59: 10846 + 187 = 11033
Step 60: 11033 + 187 = 11220
Step 61: 11220 + 187 = 11407
Step 62: 11407 + 187 = 11594
Step 63: 11594 + 187 = 11781
Step 64: 11781 + 187 = 11968
Step 65: 11968 + 187 = 12155
Step 66: 12155 + 187 = 12342
Step 67: 12342 + 187 = 12529
Step 68: 12529 + 187 = 12716
Step 69: 12716 + 187 = 12903
Step 70: 12903 + 187 = 13090
Step 71: 13090 + 187 = 13277
Step 72: 13277 + 187 = 13464
Step 73: 13464 + 187 = 13651
Step 74: 13651 + 187 = 13838
Step 75: 13838 + 187 = 14025
Step 76: 14025 + 187 = 14212
Step 77: 14212 + 187 = 14399
Step 78: 14399 + 187 = 14586
Step 79: 14586 + 187 = 14773
Step 80: 14773 + 187 = 14960
Step 81: 14960 + 187 = 15147
Step 82: 15147 + 187 = 15334
Step 83: 15334 + 187 = 15521
Step 84: 15521 + 187 = 15708
Step 85: 15708 + 187 = 15895
Step 86: 15895 + 187 = 16082
Step 87: 16082 + 187 = 16269
Step 88: 16269 + 187 = 16456
Step 89: 16456 + 187 = 16643
Step 90: 16643 + 187 = 16830
Step 91: 16830 + 187 = 17017
Step 92: 17017 + 187 = 17204
Step 93: 17204 + 187 = 17391
Step 94: 17391 + 187 = 17578
Step 95: 17578 + 187 = 17765
Step 96: 17765 + 187 = 17952
Step 97: 17952 + 187 = 18139
Step 98: 18139 + 187 = 18326
Step 99: 18326 + 187 = 18513
Step 100: 18513 + 187 = 18700
Step 101: 18700 + 187 = 18887
Step 102: 18887 + 187 = 19074
Step 103: 19074 + 187 = 19261
Step 104: 19261 + 187 = 19448
Step 105: 19448 + 187 = 19635
Step 106: 19635 + 187 = 19822
Step 107: 19822 + 187 = 20009
Step 108: 20009 + 187 = 20196
Step 109: 20196 + 187 = 20383
Step 110: 20383 + 187 = 20570
Step 111: 20570 + 187 = 20757
Step 112: 20757 + 187 = 20944
Step 113: 20944 + 187 = 21131
Step 114: 21131 + 187 = 21318
Step 115: 21318 + 187 = 21505
Step 116: 21505 + 187 = 21692
Step 117: 21692 + 187 = 21879
Step 118: 21879 + 187 = 22066
Step 119: 22066 + 187 = 22253
Step 120: 22253 + 187 = 22440
Step 121: 22440 + 187 = 22627
Step 122: 22627 + 187 = 22814
Step 123: 22814 + 187 = 23001
Step 124: 23001 + 187 = 23188
Step 125: 23188 + 187 = 23375
Step 126: 23375 + 187 = 23562
Step 127: 23562 + 187 = 23749
Step 128: 23749 + 187 = 23936
Step 129: 23936 + 187 = 24123

So, 187*129 = 24123