Out of 20 students taking a midterm psych exam, 15 answered the first of two bonus questions, 13 answered the second bonus question, 2 didn’t bother with either

Question

You have to use venn diagram to answer 

Answer 1

With 20 students, 2 didn't bother, so that's 18 left who attempted either or both of them.

15 out of 18 did question one, so that infers 3 did only question two. (18 - 15)

13 out of 18 did question two, so that infers 5 did only question one. (18 - 13)

 

That leaves us a diagram that roughly looks like this:

2   (5 ( 10 ) 3)