Sure thing! We've got 812 and we're gonna multiply it by 100. That's the same as adding 812 to itself 100 times.
Step 1: 0 + 812 = 812
Step 2: 812 + 812 = 1624
Step 3: 1624 + 812 = 2436
Step 4: 2436 + 812 = 3248
Step 5: 3248 + 812 = 4060
Step 6: 4060 + 812 = 4872
Step 7: 4872 + 812 = 5684
Step 8: 5684 + 812 = 6496
Step 9: 6496 + 812 = 7308
Step 10: 7308 + 812 = 8120
Step 11: 8120 + 812 = 8932
Step 12: 8932 + 812 = 9744
Step 13: 9744 + 812 = 10556
Step 14: 10556 + 812 = 11368
Step 15: 11368 + 812 = 12180
Step 16: 12180 + 812 = 12992
Step 17: 12992 + 812 = 13804
Step 18: 13804 + 812 = 14616
Step 19: 14616 + 812 = 15428
Step 20: 15428 + 812 = 16240
Step 21: 16240 + 812 = 17052
Step 22: 17052 + 812 = 17864
Step 23: 17864 + 812 = 18676
Step 24: 18676 + 812 = 19488
Step 25: 19488 + 812 = 20300
Step 26: 20300 + 812 = 21112
Step 27: 21112 + 812 = 21924
Step 28: 21924 + 812 = 22736
Step 29: 22736 + 812 = 23548
Step 30: 23548 + 812 = 24360
Step 31: 24360 + 812 = 25172
Step 32: 25172 + 812 = 25984
Step 33: 25984 + 812 = 26796
Step 34: 26796 + 812 = 27608
Step 35: 27608 + 812 = 28420
Step 36: 28420 + 812 = 29232
Step 37: 29232 + 812 = 30044
Step 38: 30044 + 812 = 30856
Step 39: 30856 + 812 = 31668
Step 40: 31668 + 812 = 32480
Step 41: 32480 + 812 = 33292
Step 42: 33292 + 812 = 34104
Step 43: 34104 + 812 = 34916
Step 44: 34916 + 812 = 35728
Step 45: 35728 + 812 = 36540
Step 46: 36540 + 812 = 37352
Step 47: 37352 + 812 = 38164
Step 48: 38164 + 812 = 38976
Step 49: 38976 + 812 = 39788
Step 50: 39788 + 812 = 40600
Step 51: 40600 + 812 = 41412
Step 52: 41412 + 812 = 42224
Step 53: 42224 + 812 = 43036
Step 54: 43036 + 812 = 43848
Step 55: 43848 + 812 = 44660
Step 56: 44660 + 812 = 45472
Step 57: 45472 + 812 = 46284
Step 58: 46284 + 812 = 47096
Step 59: 47096 + 812 = 47908
Step 60: 47908 + 812 = 48720
Step 61: 48720 + 812 = 49532
Step 62: 49532 + 812 = 50344
Step 63: 50344 + 812 = 51156
Step 64: 51156 + 812 = 51968
Step 65: 51968 + 812 = 52780
Step 66: 52780 + 812 = 53592
Step 67: 53592 + 812 = 54404
Step 68: 54404 + 812 = 55216
Step 69: 55216 + 812 = 56028
Step 70: 56028 + 812 = 56840
Step 71: 56840 + 812 = 57652
Step 72: 57652 + 812 = 58464
Step 73: 58464 + 812 = 59276
Step 74: 59276 + 812 = 60088
Step 75: 60088 + 812 = 60900
Step 76: 60900 + 812 = 61712
Step 77: 61712 + 812 = 62524
Step 78: 62524 + 812 = 63336
Step 79: 63336 + 812 = 64148
Step 80: 64148 + 812 = 64960
Step 81: 64960 + 812 = 65772
Step 82: 65772 + 812 = 66584
Step 83: 66584 + 812 = 67396
Step 84: 67396 + 812 = 68208
Step 85: 68208 + 812 = 69020
Step 86: 69020 + 812 = 69832
Step 87: 69832 + 812 = 70644
Step 88: 70644 + 812 = 71456
Step 89: 71456 + 812 = 72268
Step 90: 72268 + 812 = 73080
Step 91: 73080 + 812 = 73892
Step 92: 73892 + 812 = 74704
Step 93: 74704 + 812 = 75516
Step 94: 75516 + 812 = 76328
Step 95: 76328 + 812 = 77140
Step 96: 77140 + 812 = 77952
Step 97: 77952 + 812 = 78764
Step 98: 78764 + 812 = 79576
Step 99: 79576 + 812 = 80388
Step 100: 80388 + 812 = 81200

So, 812*100 = 81200