Substitute $\displaystyle{x}=-{2}\usepackage{cmbright}\Huge\$ and $\displaystyle{y}=-{4}\usepackage{cmbright}\Huge\$ into the equation: $\displaystyle{6}{\left(-{2}\right)}-{4}{\left(-{4}\right)}={4}\usepackage{cmbright}\Huge\$

Simplify: $\displaystyle-{12}+{16}={4}\usepackage{cmbright}\Huge\$ or $\displaystyle{4}={4}\usepackage{cmbright}\Huge\$

The statement is true, so $\displaystyle{\left(-{2},-{4}\right)}\usepackage{cmbright}\Huge\$ is a solution to the equation.