Subtract 12 from both sides of the first inequality to get $\displaystyle{3}{m}>{21}\usepackage{cmbright}\Huge\$ . Then divide both sides by 3 to get $\displaystyle{m}>{7}\usepackage{cmbright}\Huge\$ . Divide both sides of the second inequality by $\displaystyle-{4}\usepackage{cmbright}\Huge\$ and reverse the inequality symbol to get $\displaystyle{m}\le-{8}\usepackage{cmbright}\Huge\$ . Since the graphs of $\displaystyle{m}>{7}\usepackage{cmbright}\Huge\$ and $\displaystyle{m}\le-{8}\usepackage{cmbright}\Huge\$ have no overlap, there is no solution.