During the first stage of the division process, when you subtracted $\displaystyle{4}{x}-{\left(-{3}{x}\right)}\usepackage{cmbright}\Huge\$ , you may have mistakenly gotten $\displaystyle-{7}{x}\usepackage{cmbright}\Huge\$ as a result, when it should actually be $\displaystyle{7}{x}\usepackage{cmbright}\Huge\$ .