When $\displaystyle{x}={2}\usepackage{cmbright}\Huge\$ , $\displaystyle{20}-{2}{x}={20}-{2}\cdot{2}={20}-{4}={16}\usepackage{cmbright}\Huge\$ . When $\displaystyle{x}={3}\usepackage{cmbright}\Huge\$ , $\displaystyle{20}-{2}{x}={20}-{2}\cdot{3}={20}-{6}={14}\usepackage{cmbright}\Huge\$ .