Many use the calculator to find this answer, which is 0.0714285 . But if you need to do it on a piece of paper but don't want to, it's 14.
14
5
2
0.0333
14.7586
20 divided into 420 = 0.047619047619047616
420 divided by4 = 105
70
2/3 divided by 420 = 2/(3*420) = 2/1260 = 0.00587
0.0476
420
30% off $420 = $420 - (0.3 x $420) = 294
8.9362
0.015
60