Use the union rule to answer.

If n(A) = 10, n(B) = 15 and n(a ∩ B) = 9, what is n(A U B)?

**Solution:-**

The union rule for sets is symbolized n(A U B) = n(A) + n(B) – n(A ∩B). For this problem, you are given all the numbers necessary to apply the formula.

n(A) = 10

n(B) = 15

n(A ∩ B) = 9

Substitute each number into the formula.

n(A U B) = n(A) + n(B) – n(A ∩ B)

n(A U B) = 10 + 15 – 9

=16