Jika n(A)=12, n(A irisan B)=5 dan n(A U B)=20 maka n(B) adalah....

n (A U B) = n(A) + n(B) - n(A iris B)
20 = 12 + n(B) - 5
20 = 7 + n(B)
7 + n(B) = 20
n(B) = 20 - 7
n(B) = 13

Bab Himpunan
Matematika SMP Kelas VIII

n(A U B) = n(A) + n(B) - n(AnB) = 20
12 + n(B) - 5 = 20
n(B) = 20 - 7
n(B) = 13