Let's roll up our sleeves and solve this. We have 127 and we're going to multiply it by 129, essentially adding 127 to itself 129 times.
Step 1: 0 + 127 = 127
Step 2: 127 + 127 = 254
Step 3: 254 + 127 = 381
Step 4: 381 + 127 = 508
Step 5: 508 + 127 = 635
Step 6: 635 + 127 = 762
Step 7: 762 + 127 = 889
Step 8: 889 + 127 = 1016
Step 9: 1016 + 127 = 1143
Step 10: 1143 + 127 = 1270
Step 11: 1270 + 127 = 1397
Step 12: 1397 + 127 = 1524
Step 13: 1524 + 127 = 1651
Step 14: 1651 + 127 = 1778
Step 15: 1778 + 127 = 1905
Step 16: 1905 + 127 = 2032
Step 17: 2032 + 127 = 2159
Step 18: 2159 + 127 = 2286
Step 19: 2286 + 127 = 2413
Step 20: 2413 + 127 = 2540
Step 21: 2540 + 127 = 2667
Step 22: 2667 + 127 = 2794
Step 23: 2794 + 127 = 2921
Step 24: 2921 + 127 = 3048
Step 25: 3048 + 127 = 3175
Step 26: 3175 + 127 = 3302
Step 27: 3302 + 127 = 3429
Step 28: 3429 + 127 = 3556
Step 29: 3556 + 127 = 3683
Step 30: 3683 + 127 = 3810
Step 31: 3810 + 127 = 3937
Step 32: 3937 + 127 = 4064
Step 33: 4064 + 127 = 4191
Step 34: 4191 + 127 = 4318
Step 35: 4318 + 127 = 4445
Step 36: 4445 + 127 = 4572
Step 37: 4572 + 127 = 4699
Step 38: 4699 + 127 = 4826
Step 39: 4826 + 127 = 4953
Step 40: 4953 + 127 = 5080
Step 41: 5080 + 127 = 5207
Step 42: 5207 + 127 = 5334
Step 43: 5334 + 127 = 5461
Step 44: 5461 + 127 = 5588
Step 45: 5588 + 127 = 5715
Step 46: 5715 + 127 = 5842
Step 47: 5842 + 127 = 5969
Step 48: 5969 + 127 = 6096
Step 49: 6096 + 127 = 6223
Step 50: 6223 + 127 = 6350
Step 51: 6350 + 127 = 6477
Step 52: 6477 + 127 = 6604
Step 53: 6604 + 127 = 6731
Step 54: 6731 + 127 = 6858
Step 55: 6858 + 127 = 6985
Step 56: 6985 + 127 = 7112
Step 57: 7112 + 127 = 7239
Step 58: 7239 + 127 = 7366
Step 59: 7366 + 127 = 7493
Step 60: 7493 + 127 = 7620
Step 61: 7620 + 127 = 7747
Step 62: 7747 + 127 = 7874
Step 63: 7874 + 127 = 8001
Step 64: 8001 + 127 = 8128
Step 65: 8128 + 127 = 8255
Step 66: 8255 + 127 = 8382
Step 67: 8382 + 127 = 8509
Step 68: 8509 + 127 = 8636
Step 69: 8636 + 127 = 8763
Step 70: 8763 + 127 = 8890
Step 71: 8890 + 127 = 9017
Step 72: 9017 + 127 = 9144
Step 73: 9144 + 127 = 9271
Step 74: 9271 + 127 = 9398
Step 75: 9398 + 127 = 9525
Step 76: 9525 + 127 = 9652
Step 77: 9652 + 127 = 9779
Step 78: 9779 + 127 = 9906
Step 79: 9906 + 127 = 10033
Step 80: 10033 + 127 = 10160
Step 81: 10160 + 127 = 10287
Step 82: 10287 + 127 = 10414
Step 83: 10414 + 127 = 10541
Step 84: 10541 + 127 = 10668
Step 85: 10668 + 127 = 10795
Step 86: 10795 + 127 = 10922
Step 87: 10922 + 127 = 11049
Step 88: 11049 + 127 = 11176
Step 89: 11176 + 127 = 11303
Step 90: 11303 + 127 = 11430
Step 91: 11430 + 127 = 11557
Step 92: 11557 + 127 = 11684
Step 93: 11684 + 127 = 11811
Step 94: 11811 + 127 = 11938
Step 95: 11938 + 127 = 12065
Step 96: 12065 + 127 = 12192
Step 97: 12192 + 127 = 12319
Step 98: 12319 + 127 = 12446
Step 99: 12446 + 127 = 12573
Step 100: 12573 + 127 = 12700
Step 101: 12700 + 127 = 12827
Step 102: 12827 + 127 = 12954
Step 103: 12954 + 127 = 13081
Step 104: 13081 + 127 = 13208
Step 105: 13208 + 127 = 13335
Step 106: 13335 + 127 = 13462
Step 107: 13462 + 127 = 13589
Step 108: 13589 + 127 = 13716
Step 109: 13716 + 127 = 13843
Step 110: 13843 + 127 = 13970
Step 111: 13970 + 127 = 14097
Step 112: 14097 + 127 = 14224
Step 113: 14224 + 127 = 14351
Step 114: 14351 + 127 = 14478
Step 115: 14478 + 127 = 14605
Step 116: 14605 + 127 = 14732
Step 117: 14732 + 127 = 14859
Step 118: 14859 + 127 = 14986
Step 119: 14986 + 127 = 15113
Step 120: 15113 + 127 = 15240
Step 121: 15240 + 127 = 15367
Step 122: 15367 + 127 = 15494
Step 123: 15494 + 127 = 15621
Step 124: 15621 + 127 = 15748
Step 125: 15748 + 127 = 15875
Step 126: 15875 + 127 = 16002
Step 127: 16002 + 127 = 16129
Step 128: 16129 + 127 = 16256
Step 129: 16256 + 127 = 16383

So, 127*129 = 16383