Let's get this math done. We have 811 and we're going to multiply it by 15. This is the same as taking 811 and adding it to itself 15 times.
Step 1: 0 + 811 = 811
Step 2: 811 + 811 = 1622
Step 3: 1622 + 811 = 2433
Step 4: 2433 + 811 = 3244
Step 5: 3244 + 811 = 4055
Step 6: 4055 + 811 = 4866
Step 7: 4866 + 811 = 5677
Step 8: 5677 + 811 = 6488
Step 9: 6488 + 811 = 7299
Step 10: 7299 + 811 = 8110
Step 11: 8110 + 811 = 8921
Step 12: 8921 + 811 = 9732
Step 13: 9732 + 811 = 10543
Step 14: 10543 + 811 = 11354
Step 15: 11354 + 811 = 12165

So, 811*15 = 12165