You may have forgotten to reverse the inequality symbol when dividing both sides of the first inequality by a negative number. The solution to the first inequality is $\displaystyle{t}\le-{2}\usepackage{cmbright}\Huge\$ . The solution to the second inequality is $\displaystyle{t}\ge-{7}\usepackage{cmbright}\Huge\$ . The solution to the compound inequality is the overlap of these two solutions.

The correct answer is $\displaystyle-{7}\le{t}\le-{2}\usepackage{cmbright}\Huge\$ .