Add the equations to get: $\displaystyle{10}{x}={60}\usepackage{cmbright}\Huge\$

Solve for x to get $\displaystyle{x}={6}\usepackage{cmbright}\Huge\$ and substitute into the second equation:

$\displaystyle{6}+{2}{y}={14}\usepackage{cmbright}\Huge\$ , so $\displaystyle{2}{y}={8}\usepackage{cmbright}\Huge\$ and $\displaystyle{y}={4}\usepackage{cmbright}\Huge\$