OK, let's crack this. We're given 677 and our task is to multiply it by 15. Essentially, we'll be adding 677 to itself 15 times.
Step 1: 0 + 677 = 677
Step 2: 677 + 677 = 1354
Step 3: 1354 + 677 = 2031
Step 4: 2031 + 677 = 2708
Step 5: 2708 + 677 = 3385
Step 6: 3385 + 677 = 4062
Step 7: 4062 + 677 = 4739
Step 8: 4739 + 677 = 5416
Step 9: 5416 + 677 = 6093
Step 10: 6093 + 677 = 6770
Step 11: 6770 + 677 = 7447
Step 12: 7447 + 677 = 8124
Step 13: 8124 + 677 = 8801
Step 14: 8801 + 677 = 9478
Step 15: 9478 + 677 = 10155

So, 677*15 = 10155