Let's get this math done. We have 687 and we're going to multiply it by 15. This is the same as taking 687 and adding it to itself 15 times.
Step 1: 0 + 687 = 687
Step 2: 687 + 687 = 1374
Step 3: 1374 + 687 = 2061
Step 4: 2061 + 687 = 2748
Step 5: 2748 + 687 = 3435
Step 6: 3435 + 687 = 4122
Step 7: 4122 + 687 = 4809
Step 8: 4809 + 687 = 5496
Step 9: 5496 + 687 = 6183
Step 10: 6183 + 687 = 6870
Step 11: 6870 + 687 = 7557
Step 12: 7557 + 687 = 8244
Step 13: 8244 + 687 = 8931
Step 14: 8931 + 687 = 9618
Step 15: 9618 + 687 = 10305

So, 687*15 = 10305