OK, let's work through this together. We're starting with 798 and we're going to multiply it by 16, which means we add 798 to itself 16 times.
Step 1: 0 + 798 = 798
Step 2: 798 + 798 = 1596
Step 3: 1596 + 798 = 2394
Step 4: 2394 + 798 = 3192
Step 5: 3192 + 798 = 3990
Step 6: 3990 + 798 = 4788
Step 7: 4788 + 798 = 5586
Step 8: 5586 + 798 = 6384
Step 9: 6384 + 798 = 7182
Step 10: 7182 + 798 = 7980
Step 11: 7980 + 798 = 8778
Step 12: 8778 + 798 = 9576
Step 13: 9576 + 798 = 10374
Step 14: 10374 + 798 = 11172
Step 15: 11172 + 798 = 11970
Step 16: 11970 + 798 = 12768

So, 798*16 = 12768