You may have correctly rewritten the equation as $\displaystyle{{\left({5}{x}-{2}\right)}}^{{2}}={45}\usepackage{cmbright}\Huge\$ , and then mistakenly thought that if you divided by 5 you would get $\displaystyle{{\left({x}-\frac{{2}}{{5}}\right)}}^{{2}}={9}\usepackage{cmbright}\Huge\$ . This is the result of an incorrect order of operations. Instead, use the Square Root Property to get $\displaystyle{5}{x}-{2}=\pm\sqrt{{45}}\usepackage{cmbright}\Huge\$ , simplify the radical, and solve for x.