Though you found the correct slope of the line, you made a mistake when finding b. After substituting the point $\displaystyle{\left(-{6},-{2}\right)}\usepackage{cmbright}\Huge\$ for x and y in $\displaystyle{y}={2}{x}+{b}\usepackage{cmbright}\Huge\$ , you incorrectly subtracted 12 instead of adding 12 to both sides of the equation.