You may have correctly chosen to subtract 9 from both sides, but then made a mistake with the subtraction of $\displaystyle{5}-{9}\usepackage{cmbright}\Huge\$ . Remember that subtraction is the same as adding the opposite number, and the sign of the result is the sign of the number with the greater absolute value. The correct answer is $\displaystyle{n}\le-{4}\usepackage{cmbright}\Huge\$ .