You correctly substituted the slope $\displaystyle\frac{{3}}{{2}}\usepackage{cmbright}\Huge\$ into the equation $\displaystyle{y}={m}{x}+{b}\usepackage{cmbright}\Huge\$ . However, when you substituted $\displaystyle{\left(-{2},-{4}\right)}\usepackage{cmbright}\Huge\$ into the equation to find b, you mixed up the x-value and the y-value.