If n(A u B ) = 25 , n(A)=12, n(A-B)=8 then find the number of elements in AnB

If n(A u B ) = 25 , n(A)=12, n(A-B)=8 then find the number of elements

1.	If n(A u B ) = 25 , n(A)=12, n(A-B)=8 then find the number of elements in AnB
Answer» n (A)=n (A-B)+n (AnB), n (AnB)=n (A)-n (A-B), n (AnB)=12-8=4, n (AnB)=4