Given n(U)=20,n(A)=12,n(B)=9,n(A∩B)=4, where U is the universal set, A and B are subsets of U, then n(A∪B)C=
17
9
11
3
n(A∪B)=n(A)+n(B)−n(A∩B)=12+9−4=17 Now, n(A∪B)c=n(U)−n(A∪B)=20−17=3