You solved $\displaystyle{4}{\left|{m}-{5}\right|}-{4}>{20}\usepackage{cmbright}\Huge\$ , instead of $\displaystyle{4}{\left|{m}-{5}\right|}-{4}<{20}\usepackage{cmbright}\Huge\$ . You should first simplify to $\displaystyle{\left|{m}-{5}\right|}<{6}\usepackage{cmbright}\Huge\$ , and then rewrite without absolute value as $\displaystyle-{6}<{m}-{5}<{6}\usepackage{cmbright}\Huge\$ . The correct answer is $\displaystyle-{1}<{m}<{11}\usepackage{cmbright}\Huge\$ .