It seems that you multiplied by $\displaystyle-{5}\usepackage{cmbright}\Huge\$ instead of dividing both sides of the equation by $\displaystyle-{5}\usepackage{cmbright}\Huge\$ . Multiplying $\displaystyle-{5}{x}\usepackage{cmbright}\Huge\$ by $\displaystyle-{5}\usepackage{cmbright}\Huge\$ will not leave you with x, and you must do the same thing to both sides.