While trying to get the variable terms together on the left side, you may have added $\displaystyle{5}{x}\usepackage{cmbright}\Huge\$ to $\displaystyle{2}{x}\usepackage{cmbright}\Huge\$ . To combine the variable terms, you would need to subtract $\displaystyle{5}{x}\usepackage{cmbright}\Huge\$ from both sides.