Let's get this math done. We have 930 and we're going to multiply it by 21. This is the same as taking 930 and adding it to itself 21 times.
Step 1: 0 + 930 = 930
Step 2: 930 + 930 = 1860
Step 3: 1860 + 930 = 2790
Step 4: 2790 + 930 = 3720
Step 5: 3720 + 930 = 4650
Step 6: 4650 + 930 = 5580
Step 7: 5580 + 930 = 6510
Step 8: 6510 + 930 = 7440
Step 9: 7440 + 930 = 8370
Step 10: 8370 + 930 = 9300
Step 11: 9300 + 930 = 10230
Step 12: 10230 + 930 = 11160
Step 13: 11160 + 930 = 12090
Step 14: 12090 + 930 = 13020
Step 15: 13020 + 930 = 13950
Step 16: 13950 + 930 = 14880
Step 17: 14880 + 930 = 15810
Step 18: 15810 + 930 = 16740
Step 19: 16740 + 930 = 17670
Step 20: 17670 + 930 = 18600
Step 21: 18600 + 930 = 19530

So, 930*21 = 19530