You may have seen that $\displaystyle{32}-{8}={24}\usepackage{cmbright}\Huge\$ and thought that $\displaystyle{28}-{n}\usepackage{cmbright}\Huge\$ was 24. You cannot simplify fractions this way. Cross multiply. After you simplify, divide both sides by 32. The correct answer is $\displaystyle{n}={7}\usepackage{cmbright}\Huge\$ .