Without delay, let's solve this. We've got 667 and we will be multiplying it by 20, that is, adding 667 to itself 20 times.
Step 1: 0 + 667 = 667
Step 2: 667 + 667 = 1334
Step 3: 1334 + 667 = 2001
Step 4: 2001 + 667 = 2668
Step 5: 2668 + 667 = 3335
Step 6: 3335 + 667 = 4002
Step 7: 4002 + 667 = 4669
Step 8: 4669 + 667 = 5336
Step 9: 5336 + 667 = 6003
Step 10: 6003 + 667 = 6670
Step 11: 6670 + 667 = 7337
Step 12: 7337 + 667 = 8004
Step 13: 8004 + 667 = 8671
Step 14: 8671 + 667 = 9338
Step 15: 9338 + 667 = 10005
Step 16: 10005 + 667 = 10672
Step 17: 10672 + 667 = 11339
Step 18: 11339 + 667 = 12006
Step 19: 12006 + 667 = 12673
Step 20: 12673 + 667 = 13340

So, 667*20 = 13340