Let U be a Universal set and n(U)=12. If A,B⊆U are such that n(B)=6 and n(A∩B)=2 then n(A∪B') is equal to
6
10
7
8
n(A∪B')=n(A)+n(B')-n(A∩B')=n(A)+n(U)-n(B)-(n(A)-n(A∩B)) =n(U)-n(B)+n(A∩B) =12-6+2=8.