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

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

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

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