Sure thing! We've got 668 and we're gonna multiply it by 15. That's the same as adding 668 to itself 15 times.
Step 1: 0 + 668 = 668
Step 2: 668 + 668 = 1336
Step 3: 1336 + 668 = 2004
Step 4: 2004 + 668 = 2672
Step 5: 2672 + 668 = 3340
Step 6: 3340 + 668 = 4008
Step 7: 4008 + 668 = 4676
Step 8: 4676 + 668 = 5344
Step 9: 5344 + 668 = 6012
Step 10: 6012 + 668 = 6680
Step 11: 6680 + 668 = 7348
Step 12: 7348 + 668 = 8016
Step 13: 8016 + 668 = 8684
Step 14: 8684 + 668 = 9352
Step 15: 9352 + 668 = 10020

So, 668*15 = 10020