OK, let's crack this. We're given 685 and our task is to multiply it by 15. Essentially, we'll be adding 685 to itself 15 times.
Step 1: 0 + 685 = 685
Step 2: 685 + 685 = 1370
Step 3: 1370 + 685 = 2055
Step 4: 2055 + 685 = 2740
Step 5: 2740 + 685 = 3425
Step 6: 3425 + 685 = 4110
Step 7: 4110 + 685 = 4795
Step 8: 4795 + 685 = 5480
Step 9: 5480 + 685 = 6165
Step 10: 6165 + 685 = 6850
Step 11: 6850 + 685 = 7535
Step 12: 7535 + 685 = 8220
Step 13: 8220 + 685 = 8905
Step 14: 8905 + 685 = 9590
Step 15: 9590 + 685 = 10275

So, 685*15 = 10275