Question

Let A and B be subsets of a universal set U and suppose n(U) = 200, n(a)=100, n(B)=80, and n(A intercept B)=40.

Of 100 clock radios with digital tuners and / or CD players sold recently in a department store, 70 had digital; tuners and 90 and CD players. How many radios had both digital tuners and CD players?