OK, let's crack this. We're given 336 and our task is to multiply it by 20. Essentially, we'll be adding 336 to itself 20 times.
Step 1: 0 + 336 = 336
Step 2: 336 + 336 = 672
Step 3: 672 + 336 = 1008
Step 4: 1008 + 336 = 1344
Step 5: 1344 + 336 = 1680
Step 6: 1680 + 336 = 2016
Step 7: 2016 + 336 = 2352
Step 8: 2352 + 336 = 2688
Step 9: 2688 + 336 = 3024
Step 10: 3024 + 336 = 3360
Step 11: 3360 + 336 = 3696
Step 12: 3696 + 336 = 4032
Step 13: 4032 + 336 = 4368
Step 14: 4368 + 336 = 4704
Step 15: 4704 + 336 = 5040
Step 16: 5040 + 336 = 5376
Step 17: 5376 + 336 = 5712
Step 18: 5712 + 336 = 6048
Step 19: 6048 + 336 = 6384
Step 20: 6384 + 336 = 6720

So, 336*20 = 6720