Question

For this exercise, let A and B be subsets of a universal set U and suppose n(U)= 200, n(A)= 100, n(B)= 80, and n (A∩B)=40. Compute:
n (A U B)

For this exercise would I compute it by using the addition rule?
n(A U B) = n(A) +n(B) - n (A ∩ B)
n(A U B) = 100 + 80 - 40
=180-40=140
n(AUB) =140