Question

If n(A) = 12, n(B) = 17 and (\n(A \cup B) = 21 \), then $n(A\cap B)$ is equal to ___.

Answer 1

Given that n(A) = 12, n(B) = 17 and $n(A\cup B)=21$

By using the formula n(A $\cup$ B) = n(A) + n(B) - n(A $\cap$ B)

n(A $\cap$ B) = 12 + 17 - 21= 8