This is a solution to the second equation, but not to the system. If you substitute these values into the first equation you get $\displaystyle{14}={2}+{7}{\left(-{4}\right)}\usepackage{cmbright}\Huge\$ , or $\displaystyle{14}={2}-{28}\usepackage{cmbright}\Huge\$ , which is false. Substitute $\displaystyle{2}+{7}{x}\usepackage{cmbright}\Huge\$ for y in the second equation and solve for x. Substitute this value into any equation to find y.