The line $\displaystyle{y}+{2}{x}={9}\usepackage{cmbright}\Huge\$ is graphed correctly, but the other line is not. The point of intersection should be the solution to the system, $\displaystyle{\left({6},-{3}\right)}\usepackage{cmbright}\Huge\$ . However, the point of intersection that is pictured is $\displaystyle{\left({3},{3}\right)}\usepackage{cmbright}\Huge\$ . The correct graph of $\displaystyle{4}{y}+{x}=-{6}\usepackage{cmbright}\Huge\$ goes through $\displaystyle{\left(-{6},{0}\right)}\usepackage{cmbright}\Huge\$ and $\displaystyle{\left({6},-{3}\right)}\usepackage{cmbright}\Huge\$ .