Explanation:
You are finding the whole
0.7 Ă— 20 = 14
or
70% of 20 = 7/10 x 20 = 7/10 x 20/1 = 140/10
140/10
140/10 = 14/1
The minimum number of questions he need to do are 14
I'm not sure if you are finding the part or the whole
let me know if im wrong