During the first stage of the division process, when you should have subtracted $\displaystyle{3}{x}-{\left(-{7}{x}\right)}\usepackage{cmbright}\Huge\$ , you may have added $\displaystyle{3}{x}\usepackage{cmbright}\Huge\$ and $\displaystyle-{7}{x}\usepackage{cmbright}\Huge\$ . This would have given you $\displaystyle-{4}{x}-{7}\usepackage{cmbright}\Huge\$ left over for the next stage, when you should have had $\displaystyle{10}{x}-{7}\usepackage{cmbright}\Huge\$ . Make sure that you distribute the minus sign when you get to the steps involving subtraction. The correct answer is 63.