OK, let's crack this. We're given 111 and our task is to multiply it by 15. Essentially, we'll be adding 111 to itself 15 times.
Step 1: 0 + 111 = 111
Step 2: 111 + 111 = 222
Step 3: 222 + 111 = 333
Step 4: 333 + 111 = 444
Step 5: 444 + 111 = 555
Step 6: 555 + 111 = 666
Step 7: 666 + 111 = 777
Step 8: 777 + 111 = 888
Step 9: 888 + 111 = 999
Step 10: 999 + 111 = 1110
Step 11: 1110 + 111 = 1221
Step 12: 1221 + 111 = 1332
Step 13: 1332 + 111 = 1443
Step 14: 1443 + 111 = 1554
Step 15: 1554 + 111 = 1665

So, 111*15 = 1665