This is a solution to the first equation, but not to the system. If you substitute these values into the second equation you get $\displaystyle-{3}={4}-{2}{\left(-{6}\right)}\usepackage{cmbright}\Huge\$ , or $\displaystyle-{3}={4}+{12}\usepackage{cmbright}\Huge\$ , which is false. Substitute $\displaystyle{4}-{2}{y}\usepackage{cmbright}\Huge\$ for x in the first equation and solve for y. Substitute this value into any equation to find x.