OK, let's work through this together. We're starting with 51 and we're going to multiply it by 16, which means we add 51 to itself 16 times.
Step 1: 0 + 51 = 51
Step 2: 51 + 51 = 102
Step 3: 102 + 51 = 153
Step 4: 153 + 51 = 204
Step 5: 204 + 51 = 255
Step 6: 255 + 51 = 306
Step 7: 306 + 51 = 357
Step 8: 357 + 51 = 408
Step 9: 408 + 51 = 459
Step 10: 459 + 51 = 510
Step 11: 510 + 51 = 561
Step 12: 561 + 51 = 612
Step 13: 612 + 51 = 663
Step 14: 663 + 51 = 714
Step 15: 714 + 51 = 765
Step 16: 765 + 51 = 816

So, 51*16 = 816