OK, let's crack this. We're given 670 and our task is to multiply it by 20. Essentially, we'll be adding 670 to itself 20 times.
Step 1: 0 + 670 = 670
Step 2: 670 + 670 = 1340
Step 3: 1340 + 670 = 2010
Step 4: 2010 + 670 = 2680
Step 5: 2680 + 670 = 3350
Step 6: 3350 + 670 = 4020
Step 7: 4020 + 670 = 4690
Step 8: 4690 + 670 = 5360
Step 9: 5360 + 670 = 6030
Step 10: 6030 + 670 = 6700
Step 11: 6700 + 670 = 7370
Step 12: 7370 + 670 = 8040
Step 13: 8040 + 670 = 8710
Step 14: 8710 + 670 = 9380
Step 15: 9380 + 670 = 10050
Step 16: 10050 + 670 = 10720
Step 17: 10720 + 670 = 11390
Step 18: 11390 + 670 = 12060
Step 19: 12060 + 670 = 12730
Step 20: 12730 + 670 = 13400

So, 670*20 = 13400