Let's roll up our sleeves and solve this. We have 967 and we're going to multiply it by 21, essentially adding 967 to itself 21 times.
Step 1: 0 + 967 = 967
Step 2: 967 + 967 = 1934
Step 3: 1934 + 967 = 2901
Step 4: 2901 + 967 = 3868
Step 5: 3868 + 967 = 4835
Step 6: 4835 + 967 = 5802
Step 7: 5802 + 967 = 6769
Step 8: 6769 + 967 = 7736
Step 9: 7736 + 967 = 8703
Step 10: 8703 + 967 = 9670
Step 11: 9670 + 967 = 10637
Step 12: 10637 + 967 = 11604
Step 13: 11604 + 967 = 12571
Step 14: 12571 + 967 = 13538
Step 15: 13538 + 967 = 14505
Step 16: 14505 + 967 = 15472
Step 17: 15472 + 967 = 16439
Step 18: 16439 + 967 = 17406
Step 19: 17406 + 967 = 18373
Step 20: 18373 + 967 = 19340
Step 21: 19340 + 967 = 20307

So, 967*21 = 20307