You probably thought that the equation simplified to $\displaystyle{\left|{b}+{4}\right|}={11}\usepackage{cmbright}\Huge\$ , and then solved $\displaystyle{b}+{4}={11}\usepackage{cmbright}\Huge\$ or $\displaystyle{b}+{4}=-{11}\usepackage{cmbright}\Huge\$ . Actually it simplifies to $\displaystyle{\left|{b}+{4}\right|}=-{11}\usepackage{cmbright}\Huge\$ .