Correct. Each x-value has a corresponding y-value that you can get by substituting for x in the equation $\displaystyle{y}=-{2}{x}\usepackage{cmbright}\Huge\$ . If you substitute $\displaystyle{x}={4}\usepackage{cmbright}\Huge\$ , you get $\displaystyle{y}=-{2}{\left({4}\right)}=-{8}\usepackage{cmbright}\Huge\$ . The missing value of y is $\displaystyle-{8}\usepackage{cmbright}\Huge\$ .