You may have thought that the $\displaystyle-{24}\usepackage{cmbright}\Huge\$ and the 24 canceled out. Instead, you need to add 24 to both sides to get $\displaystyle{{\left({x}+{7}\right)}}^{{2}}={48}\usepackage{cmbright}\Huge\$ . Take the square root of both sides, isolate x, and simplify the radical. The correct answer is $\displaystyle{x}=-{7}\pm{4}\sqrt{{3}}\usepackage{cmbright}\Huge\$ .