Substitute $\displaystyle{\left({2},-{1}\right)}\usepackage{cmbright}\Huge\$ for x and y in the inequality: $\displaystyle{3}{\left({2}\right)}-{4}{\left(-{1}\right)}<{12}\usepackage{cmbright}\Huge\$

Simplify: $\displaystyle{6}+{4}<{12}\usepackage{cmbright}\Huge\$ or $\displaystyle{10}<{12}\usepackage{cmbright}\Huge\$

The statement is true, so $\displaystyle{\left({2},-{1}\right)}\usepackage{cmbright}\Huge\$ is a solution to the inequality.