OK, let's work through this together. We're starting with 921 and we're going to multiply it by 141, which means we add 921 to itself 141 times.
Step 1: 0 + 921 = 921
Step 2: 921 + 921 = 1842
Step 3: 1842 + 921 = 2763
Step 4: 2763 + 921 = 3684
Step 5: 3684 + 921 = 4605
Step 6: 4605 + 921 = 5526
Step 7: 5526 + 921 = 6447
Step 8: 6447 + 921 = 7368
Step 9: 7368 + 921 = 8289
Step 10: 8289 + 921 = 9210
Step 11: 9210 + 921 = 10131
Step 12: 10131 + 921 = 11052
Step 13: 11052 + 921 = 11973
Step 14: 11973 + 921 = 12894
Step 15: 12894 + 921 = 13815
Step 16: 13815 + 921 = 14736
Step 17: 14736 + 921 = 15657
Step 18: 15657 + 921 = 16578
Step 19: 16578 + 921 = 17499
Step 20: 17499 + 921 = 18420
Step 21: 18420 + 921 = 19341
Step 22: 19341 + 921 = 20262
Step 23: 20262 + 921 = 21183
Step 24: 21183 + 921 = 22104
Step 25: 22104 + 921 = 23025
Step 26: 23025 + 921 = 23946
Step 27: 23946 + 921 = 24867
Step 28: 24867 + 921 = 25788
Step 29: 25788 + 921 = 26709
Step 30: 26709 + 921 = 27630
Step 31: 27630 + 921 = 28551
Step 32: 28551 + 921 = 29472
Step 33: 29472 + 921 = 30393
Step 34: 30393 + 921 = 31314
Step 35: 31314 + 921 = 32235
Step 36: 32235 + 921 = 33156
Step 37: 33156 + 921 = 34077
Step 38: 34077 + 921 = 34998
Step 39: 34998 + 921 = 35919
Step 40: 35919 + 921 = 36840
Step 41: 36840 + 921 = 37761
Step 42: 37761 + 921 = 38682
Step 43: 38682 + 921 = 39603
Step 44: 39603 + 921 = 40524
Step 45: 40524 + 921 = 41445
Step 46: 41445 + 921 = 42366
Step 47: 42366 + 921 = 43287
Step 48: 43287 + 921 = 44208
Step 49: 44208 + 921 = 45129
Step 50: 45129 + 921 = 46050
Step 51: 46050 + 921 = 46971
Step 52: 46971 + 921 = 47892
Step 53: 47892 + 921 = 48813
Step 54: 48813 + 921 = 49734
Step 55: 49734 + 921 = 50655
Step 56: 50655 + 921 = 51576
Step 57: 51576 + 921 = 52497
Step 58: 52497 + 921 = 53418
Step 59: 53418 + 921 = 54339
Step 60: 54339 + 921 = 55260
Step 61: 55260 + 921 = 56181
Step 62: 56181 + 921 = 57102
Step 63: 57102 + 921 = 58023
Step 64: 58023 + 921 = 58944
Step 65: 58944 + 921 = 59865
Step 66: 59865 + 921 = 60786
Step 67: 60786 + 921 = 61707
Step 68: 61707 + 921 = 62628
Step 69: 62628 + 921 = 63549
Step 70: 63549 + 921 = 64470
Step 71: 64470 + 921 = 65391
Step 72: 65391 + 921 = 66312
Step 73: 66312 + 921 = 67233
Step 74: 67233 + 921 = 68154
Step 75: 68154 + 921 = 69075
Step 76: 69075 + 921 = 69996
Step 77: 69996 + 921 = 70917
Step 78: 70917 + 921 = 71838
Step 79: 71838 + 921 = 72759
Step 80: 72759 + 921 = 73680
Step 81: 73680 + 921 = 74601
Step 82: 74601 + 921 = 75522
Step 83: 75522 + 921 = 76443
Step 84: 76443 + 921 = 77364
Step 85: 77364 + 921 = 78285
Step 86: 78285 + 921 = 79206
Step 87: 79206 + 921 = 80127
Step 88: 80127 + 921 = 81048
Step 89: 81048 + 921 = 81969
Step 90: 81969 + 921 = 82890
Step 91: 82890 + 921 = 83811
Step 92: 83811 + 921 = 84732
Step 93: 84732 + 921 = 85653
Step 94: 85653 + 921 = 86574
Step 95: 86574 + 921 = 87495
Step 96: 87495 + 921 = 88416
Step 97: 88416 + 921 = 89337
Step 98: 89337 + 921 = 90258
Step 99: 90258 + 921 = 91179
Step 100: 91179 + 921 = 92100
Step 101: 92100 + 921 = 93021
Step 102: 93021 + 921 = 93942
Step 103: 93942 + 921 = 94863
Step 104: 94863 + 921 = 95784
Step 105: 95784 + 921 = 96705
Step 106: 96705 + 921 = 97626
Step 107: 97626 + 921 = 98547
Step 108: 98547 + 921 = 99468
Step 109: 99468 + 921 = 100389
Step 110: 100389 + 921 = 101310
Step 111: 101310 + 921 = 102231
Step 112: 102231 + 921 = 103152
Step 113: 103152 + 921 = 104073
Step 114: 104073 + 921 = 104994
Step 115: 104994 + 921 = 105915
Step 116: 105915 + 921 = 106836
Step 117: 106836 + 921 = 107757
Step 118: 107757 + 921 = 108678
Step 119: 108678 + 921 = 109599
Step 120: 109599 + 921 = 110520
Step 121: 110520 + 921 = 111441
Step 122: 111441 + 921 = 112362
Step 123: 112362 + 921 = 113283
Step 124: 113283 + 921 = 114204
Step 125: 114204 + 921 = 115125
Step 126: 115125 + 921 = 116046
Step 127: 116046 + 921 = 116967
Step 128: 116967 + 921 = 117888
Step 129: 117888 + 921 = 118809
Step 130: 118809 + 921 = 119730
Step 131: 119730 + 921 = 120651
Step 132: 120651 + 921 = 121572
Step 133: 121572 + 921 = 122493
Step 134: 122493 + 921 = 123414
Step 135: 123414 + 921 = 124335
Step 136: 124335 + 921 = 125256
Step 137: 125256 + 921 = 126177
Step 138: 126177 + 921 = 127098
Step 139: 127098 + 921 = 128019
Step 140: 128019 + 921 = 128940
Step 141: 128940 + 921 = 129861

So, 921*141 = 129861