You may have made two mistakes. While trying to get the constant terms together on the right side, you may have subtracted 11 from 16. To combine the constant terms, you would need to add 11 to both sides. While trying to get the variable terms together on the left side, you may have added $\displaystyle{7}{x}\usepackage{cmbright}\Huge\$ to $\displaystyle{2}{x}\usepackage{cmbright}\Huge\$ . To combine the variable terms, you would need to subtract $\displaystyle{7}{x}\usepackage{cmbright}\Huge\$ from both sides.