Chapter 2.3B, Problem 12A

Assessment

a. If $n\left(A\cup B\right)=23$, $n\left(A\cap B\right)=9$, and $n\left(B\right)=12$, find $n\left(A\right)$.

b. If $n\left(A\right)=9$, $n\left(B\right)=13$ and $n\left(A\cap B\right)=5$, find $n\left(A\cup B\right)$.