OK, let's crack this. We're given 812 and our task is to multiply it by 50. Essentially, we'll be adding 812 to itself 50 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

So, 812*50 = 40600