OK, let's crack this. We're given 872 and our task is to multiply it by 15. Essentially, we'll be adding 872 to itself 15 times.
Step 1: 0 + 872 = 872
Step 2: 872 + 872 = 1744
Step 3: 1744 + 872 = 2616
Step 4: 2616 + 872 = 3488
Step 5: 3488 + 872 = 4360
Step 6: 4360 + 872 = 5232
Step 7: 5232 + 872 = 6104
Step 8: 6104 + 872 = 6976
Step 9: 6976 + 872 = 7848
Step 10: 7848 + 872 = 8720
Step 11: 8720 + 872 = 9592
Step 12: 9592 + 872 = 10464
Step 13: 10464 + 872 = 11336
Step 14: 11336 + 872 = 12208
Step 15: 12208 + 872 = 13080

So, 872*15 = 13080