In a class of 40 students, the number of students who passed the math exam ... ...

In a class of 40 students, the number of students who passed the math exam is equal to half the number of students who passed the science exam. Each student in the class passed at least one of the two exams. If 5 students passed both exams, then the number of students who passed the math exam is
(A)    5
(B) ...
(C) ...
(D) ...
(E) ...

*This question is included in Nova Math - Problem Set X: Word Problems