Let's get this math done. We have 831 and we're going to multiply it by 187. This is the same as taking 831 and adding it to itself 187 times.
Step 1: 0 + 831 = 831
Step 2: 831 + 831 = 1662
Step 3: 1662 + 831 = 2493
Step 4: 2493 + 831 = 3324
Step 5: 3324 + 831 = 4155
Step 6: 4155 + 831 = 4986
Step 7: 4986 + 831 = 5817
Step 8: 5817 + 831 = 6648
Step 9: 6648 + 831 = 7479
Step 10: 7479 + 831 = 8310
Step 11: 8310 + 831 = 9141
Step 12: 9141 + 831 = 9972
Step 13: 9972 + 831 = 10803
Step 14: 10803 + 831 = 11634
Step 15: 11634 + 831 = 12465
Step 16: 12465 + 831 = 13296
Step 17: 13296 + 831 = 14127
Step 18: 14127 + 831 = 14958
Step 19: 14958 + 831 = 15789
Step 20: 15789 + 831 = 16620
Step 21: 16620 + 831 = 17451
Step 22: 17451 + 831 = 18282
Step 23: 18282 + 831 = 19113
Step 24: 19113 + 831 = 19944
Step 25: 19944 + 831 = 20775
Step 26: 20775 + 831 = 21606
Step 27: 21606 + 831 = 22437
Step 28: 22437 + 831 = 23268
Step 29: 23268 + 831 = 24099
Step 30: 24099 + 831 = 24930
Step 31: 24930 + 831 = 25761
Step 32: 25761 + 831 = 26592
Step 33: 26592 + 831 = 27423
Step 34: 27423 + 831 = 28254
Step 35: 28254 + 831 = 29085
Step 36: 29085 + 831 = 29916
Step 37: 29916 + 831 = 30747
Step 38: 30747 + 831 = 31578
Step 39: 31578 + 831 = 32409
Step 40: 32409 + 831 = 33240
Step 41: 33240 + 831 = 34071
Step 42: 34071 + 831 = 34902
Step 43: 34902 + 831 = 35733
Step 44: 35733 + 831 = 36564
Step 45: 36564 + 831 = 37395
Step 46: 37395 + 831 = 38226
Step 47: 38226 + 831 = 39057
Step 48: 39057 + 831 = 39888
Step 49: 39888 + 831 = 40719
Step 50: 40719 + 831 = 41550
Step 51: 41550 + 831 = 42381
Step 52: 42381 + 831 = 43212
Step 53: 43212 + 831 = 44043
Step 54: 44043 + 831 = 44874
Step 55: 44874 + 831 = 45705
Step 56: 45705 + 831 = 46536
Step 57: 46536 + 831 = 47367
Step 58: 47367 + 831 = 48198
Step 59: 48198 + 831 = 49029
Step 60: 49029 + 831 = 49860
Step 61: 49860 + 831 = 50691
Step 62: 50691 + 831 = 51522
Step 63: 51522 + 831 = 52353
Step 64: 52353 + 831 = 53184
Step 65: 53184 + 831 = 54015
Step 66: 54015 + 831 = 54846
Step 67: 54846 + 831 = 55677
Step 68: 55677 + 831 = 56508
Step 69: 56508 + 831 = 57339
Step 70: 57339 + 831 = 58170
Step 71: 58170 + 831 = 59001
Step 72: 59001 + 831 = 59832
Step 73: 59832 + 831 = 60663
Step 74: 60663 + 831 = 61494
Step 75: 61494 + 831 = 62325
Step 76: 62325 + 831 = 63156
Step 77: 63156 + 831 = 63987
Step 78: 63987 + 831 = 64818
Step 79: 64818 + 831 = 65649
Step 80: 65649 + 831 = 66480
Step 81: 66480 + 831 = 67311
Step 82: 67311 + 831 = 68142
Step 83: 68142 + 831 = 68973
Step 84: 68973 + 831 = 69804
Step 85: 69804 + 831 = 70635
Step 86: 70635 + 831 = 71466
Step 87: 71466 + 831 = 72297
Step 88: 72297 + 831 = 73128
Step 89: 73128 + 831 = 73959
Step 90: 73959 + 831 = 74790
Step 91: 74790 + 831 = 75621
Step 92: 75621 + 831 = 76452
Step 93: 76452 + 831 = 77283
Step 94: 77283 + 831 = 78114
Step 95: 78114 + 831 = 78945
Step 96: 78945 + 831 = 79776
Step 97: 79776 + 831 = 80607
Step 98: 80607 + 831 = 81438
Step 99: 81438 + 831 = 82269
Step 100: 82269 + 831 = 83100
Step 101: 83100 + 831 = 83931
Step 102: 83931 + 831 = 84762
Step 103: 84762 + 831 = 85593
Step 104: 85593 + 831 = 86424
Step 105: 86424 + 831 = 87255
Step 106: 87255 + 831 = 88086
Step 107: 88086 + 831 = 88917
Step 108: 88917 + 831 = 89748
Step 109: 89748 + 831 = 90579
Step 110: 90579 + 831 = 91410
Step 111: 91410 + 831 = 92241
Step 112: 92241 + 831 = 93072
Step 113: 93072 + 831 = 93903
Step 114: 93903 + 831 = 94734
Step 115: 94734 + 831 = 95565
Step 116: 95565 + 831 = 96396
Step 117: 96396 + 831 = 97227
Step 118: 97227 + 831 = 98058
Step 119: 98058 + 831 = 98889
Step 120: 98889 + 831 = 99720
Step 121: 99720 + 831 = 100551
Step 122: 100551 + 831 = 101382
Step 123: 101382 + 831 = 102213
Step 124: 102213 + 831 = 103044
Step 125: 103044 + 831 = 103875
Step 126: 103875 + 831 = 104706
Step 127: 104706 + 831 = 105537
Step 128: 105537 + 831 = 106368
Step 129: 106368 + 831 = 107199
Step 130: 107199 + 831 = 108030
Step 131: 108030 + 831 = 108861
Step 132: 108861 + 831 = 109692
Step 133: 109692 + 831 = 110523
Step 134: 110523 + 831 = 111354
Step 135: 111354 + 831 = 112185
Step 136: 112185 + 831 = 113016
Step 137: 113016 + 831 = 113847
Step 138: 113847 + 831 = 114678
Step 139: 114678 + 831 = 115509
Step 140: 115509 + 831 = 116340
Step 141: 116340 + 831 = 117171
Step 142: 117171 + 831 = 118002
Step 143: 118002 + 831 = 118833
Step 144: 118833 + 831 = 119664
Step 145: 119664 + 831 = 120495
Step 146: 120495 + 831 = 121326
Step 147: 121326 + 831 = 122157
Step 148: 122157 + 831 = 122988
Step 149: 122988 + 831 = 123819
Step 150: 123819 + 831 = 124650
Step 151: 124650 + 831 = 125481
Step 152: 125481 + 831 = 126312
Step 153: 126312 + 831 = 127143
Step 154: 127143 + 831 = 127974
Step 155: 127974 + 831 = 128805
Step 156: 128805 + 831 = 129636
Step 157: 129636 + 831 = 130467
Step 158: 130467 + 831 = 131298
Step 159: 131298 + 831 = 132129
Step 160: 132129 + 831 = 132960
Step 161: 132960 + 831 = 133791
Step 162: 133791 + 831 = 134622
Step 163: 134622 + 831 = 135453
Step 164: 135453 + 831 = 136284
Step 165: 136284 + 831 = 137115
Step 166: 137115 + 831 = 137946
Step 167: 137946 + 831 = 138777
Step 168: 138777 + 831 = 139608
Step 169: 139608 + 831 = 140439
Step 170: 140439 + 831 = 141270
Step 171: 141270 + 831 = 142101
Step 172: 142101 + 831 = 142932
Step 173: 142932 + 831 = 143763
Step 174: 143763 + 831 = 144594
Step 175: 144594 + 831 = 145425
Step 176: 145425 + 831 = 146256
Step 177: 146256 + 831 = 147087
Step 178: 147087 + 831 = 147918
Step 179: 147918 + 831 = 148749
Step 180: 148749 + 831 = 149580
Step 181: 149580 + 831 = 150411
Step 182: 150411 + 831 = 151242
Step 183: 151242 + 831 = 152073
Step 184: 152073 + 831 = 152904
Step 185: 152904 + 831 = 153735
Step 186: 153735 + 831 = 154566
Step 187: 154566 + 831 = 155397

So, 831*187 = 155397