Multiply the first equation by 4: $\displaystyle{12}{x}+{4}{y}={52}\usepackage{cmbright}\Huge\$

Add this to $\displaystyle{2}{x}-{4}{y}={32}\usepackage{cmbright}\Huge\$ to get: $\displaystyle{14}{x}={84}\usepackage{cmbright}\Huge\$

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

$\displaystyle{3}{\left({6}\right)}+{y}={13}\usepackage{cmbright}\Huge\$ or $\displaystyle{18}+{y}={13}\usepackage{cmbright}\Huge\$ , so $\displaystyle{y}=-{5}\usepackage{cmbright}\Huge\$