diketahui n(A)=21,n(B)=18,dan n(AUB)=32,maka n(AgabunganB

n (AUB) = n(A) + n(B) - n(AnB)
32 = 21 + 18 - n(AnB)
32 = 39 n(AnB)
n(AnB) = 39 - 32
n(AnB) = 7

maaf kalo salah