Let's get this math done. We have 899 and we're going to multiply it by 13. This is the same as taking 899 and adding it to itself 13 times.
Step 1: 0 + 899 = 899
Step 2: 899 + 899 = 1798
Step 3: 1798 + 899 = 2697
Step 4: 2697 + 899 = 3596
Step 5: 3596 + 899 = 4495
Step 6: 4495 + 899 = 5394
Step 7: 5394 + 899 = 6293
Step 8: 6293 + 899 = 7192
Step 9: 7192 + 899 = 8091
Step 10: 8091 + 899 = 8990
Step 11: 8990 + 899 = 9889
Step 12: 9889 + 899 = 10788
Step 13: 10788 + 899 = 11687

So, 899*13 = 11687