OK, let's crack this. We're given 807 and our task is to multiply it by 66. Essentially, we'll be adding 807 to itself 66 times.
Step 1: 0 + 807 = 807
Step 2: 807 + 807 = 1614
Step 3: 1614 + 807 = 2421
Step 4: 2421 + 807 = 3228
Step 5: 3228 + 807 = 4035
Step 6: 4035 + 807 = 4842
Step 7: 4842 + 807 = 5649
Step 8: 5649 + 807 = 6456
Step 9: 6456 + 807 = 7263
Step 10: 7263 + 807 = 8070
Step 11: 8070 + 807 = 8877
Step 12: 8877 + 807 = 9684
Step 13: 9684 + 807 = 10491
Step 14: 10491 + 807 = 11298
Step 15: 11298 + 807 = 12105
Step 16: 12105 + 807 = 12912
Step 17: 12912 + 807 = 13719
Step 18: 13719 + 807 = 14526
Step 19: 14526 + 807 = 15333
Step 20: 15333 + 807 = 16140
Step 21: 16140 + 807 = 16947
Step 22: 16947 + 807 = 17754
Step 23: 17754 + 807 = 18561
Step 24: 18561 + 807 = 19368
Step 25: 19368 + 807 = 20175
Step 26: 20175 + 807 = 20982
Step 27: 20982 + 807 = 21789
Step 28: 21789 + 807 = 22596
Step 29: 22596 + 807 = 23403
Step 30: 23403 + 807 = 24210
Step 31: 24210 + 807 = 25017
Step 32: 25017 + 807 = 25824
Step 33: 25824 + 807 = 26631
Step 34: 26631 + 807 = 27438
Step 35: 27438 + 807 = 28245
Step 36: 28245 + 807 = 29052
Step 37: 29052 + 807 = 29859
Step 38: 29859 + 807 = 30666
Step 39: 30666 + 807 = 31473
Step 40: 31473 + 807 = 32280
Step 41: 32280 + 807 = 33087
Step 42: 33087 + 807 = 33894
Step 43: 33894 + 807 = 34701
Step 44: 34701 + 807 = 35508
Step 45: 35508 + 807 = 36315
Step 46: 36315 + 807 = 37122
Step 47: 37122 + 807 = 37929
Step 48: 37929 + 807 = 38736
Step 49: 38736 + 807 = 39543
Step 50: 39543 + 807 = 40350
Step 51: 40350 + 807 = 41157
Step 52: 41157 + 807 = 41964
Step 53: 41964 + 807 = 42771
Step 54: 42771 + 807 = 43578
Step 55: 43578 + 807 = 44385
Step 56: 44385 + 807 = 45192
Step 57: 45192 + 807 = 45999
Step 58: 45999 + 807 = 46806
Step 59: 46806 + 807 = 47613
Step 60: 47613 + 807 = 48420
Step 61: 48420 + 807 = 49227
Step 62: 49227 + 807 = 50034
Step 63: 50034 + 807 = 50841
Step 64: 50841 + 807 = 51648
Step 65: 51648 + 807 = 52455
Step 66: 52455 + 807 = 53262

So, 807*66 = 53262