Sure thing! We've got 521 and we're gonna multiply it by 84. That's the same as adding 521 to itself 84 times.
Step 1: 0 + 521 = 521
Step 2: 521 + 521 = 1042
Step 3: 1042 + 521 = 1563
Step 4: 1563 + 521 = 2084
Step 5: 2084 + 521 = 2605
Step 6: 2605 + 521 = 3126
Step 7: 3126 + 521 = 3647
Step 8: 3647 + 521 = 4168
Step 9: 4168 + 521 = 4689
Step 10: 4689 + 521 = 5210
Step 11: 5210 + 521 = 5731
Step 12: 5731 + 521 = 6252
Step 13: 6252 + 521 = 6773
Step 14: 6773 + 521 = 7294
Step 15: 7294 + 521 = 7815
Step 16: 7815 + 521 = 8336
Step 17: 8336 + 521 = 8857
Step 18: 8857 + 521 = 9378
Step 19: 9378 + 521 = 9899
Step 20: 9899 + 521 = 10420
Step 21: 10420 + 521 = 10941
Step 22: 10941 + 521 = 11462
Step 23: 11462 + 521 = 11983
Step 24: 11983 + 521 = 12504
Step 25: 12504 + 521 = 13025
Step 26: 13025 + 521 = 13546
Step 27: 13546 + 521 = 14067
Step 28: 14067 + 521 = 14588
Step 29: 14588 + 521 = 15109
Step 30: 15109 + 521 = 15630
Step 31: 15630 + 521 = 16151
Step 32: 16151 + 521 = 16672
Step 33: 16672 + 521 = 17193
Step 34: 17193 + 521 = 17714
Step 35: 17714 + 521 = 18235
Step 36: 18235 + 521 = 18756
Step 37: 18756 + 521 = 19277
Step 38: 19277 + 521 = 19798
Step 39: 19798 + 521 = 20319
Step 40: 20319 + 521 = 20840
Step 41: 20840 + 521 = 21361
Step 42: 21361 + 521 = 21882
Step 43: 21882 + 521 = 22403
Step 44: 22403 + 521 = 22924
Step 45: 22924 + 521 = 23445
Step 46: 23445 + 521 = 23966
Step 47: 23966 + 521 = 24487
Step 48: 24487 + 521 = 25008
Step 49: 25008 + 521 = 25529
Step 50: 25529 + 521 = 26050
Step 51: 26050 + 521 = 26571
Step 52: 26571 + 521 = 27092
Step 53: 27092 + 521 = 27613
Step 54: 27613 + 521 = 28134
Step 55: 28134 + 521 = 28655
Step 56: 28655 + 521 = 29176
Step 57: 29176 + 521 = 29697
Step 58: 29697 + 521 = 30218
Step 59: 30218 + 521 = 30739
Step 60: 30739 + 521 = 31260
Step 61: 31260 + 521 = 31781
Step 62: 31781 + 521 = 32302
Step 63: 32302 + 521 = 32823
Step 64: 32823 + 521 = 33344
Step 65: 33344 + 521 = 33865
Step 66: 33865 + 521 = 34386
Step 67: 34386 + 521 = 34907
Step 68: 34907 + 521 = 35428
Step 69: 35428 + 521 = 35949
Step 70: 35949 + 521 = 36470
Step 71: 36470 + 521 = 36991
Step 72: 36991 + 521 = 37512
Step 73: 37512 + 521 = 38033
Step 74: 38033 + 521 = 38554
Step 75: 38554 + 521 = 39075
Step 76: 39075 + 521 = 39596
Step 77: 39596 + 521 = 40117
Step 78: 40117 + 521 = 40638
Step 79: 40638 + 521 = 41159
Step 80: 41159 + 521 = 41680
Step 81: 41680 + 521 = 42201
Step 82: 42201 + 521 = 42722
Step 83: 42722 + 521 = 43243
Step 84: 43243 + 521 = 43764

So, 521*84 = 43764