Jon P. answered • 03/24/15

Harvard honors math degree, experienced tutor in math and SAT prep

Let's call N(D) the number taking Discrete Math and N(S) the number taking statistics.

N (D or S) = N(D) + N(S) - N (D and S)

Since everyone has to take at least one of the courses N (D or S) = 40.

N(D) = 28

N (D and S) = 5

So 40 = 28 + N(S) - 5 = 23 + N(S)

So N(S) = 17

5 of the 17 students taking statistics are taking both classes, so the other 12 are taking only Statistics. So the answer is 12.