Consider the Venn Diagram below.
n(A)=\displaystyle {n}{\left({A}\right)}=

n(AB)=\displaystyle {n}{\left({A}\cup{B}\right)}=

n(B)=\displaystyle {n}{\left(\overline{{{B}}}\right)}=

n(AB)=\displaystyle {n}{\left(\overline{{{A}}}\cap{B}\right)}=