Let's get this math done. We have 660 and we're going to multiply it by 13. This is the same as taking 660 and adding it to itself 13 times.
Step 1: 0 + 660 = 660
Step 2: 660 + 660 = 1320
Step 3: 1320 + 660 = 1980
Step 4: 1980 + 660 = 2640
Step 5: 2640 + 660 = 3300
Step 6: 3300 + 660 = 3960
Step 7: 3960 + 660 = 4620
Step 8: 4620 + 660 = 5280
Step 9: 5280 + 660 = 5940
Step 10: 5940 + 660 = 6600
Step 11: 6600 + 660 = 7260
Step 12: 7260 + 660 = 7920
Step 13: 7920 + 660 = 8580

So, 660*13 = 8580