Question

In a class of 80 students, 45 are good in math,15 are good in both math and english,13 are good in both math and psychology,16 are good in both english &physchology ,20are good in physchology and 9 are good in all of the three .how many of them are good in mathematics

Answer 1

26 students are good in mathematics only.

28 students are not good in any of the three courses.