When isolating the variable, make sure that you perform the same operation on both sides of the equation. For example, if you subtract $\displaystyle{3}{k}\usepackage{cmbright}\Huge\$ from the right side, you must also subtract $\displaystyle{3}{k}\usepackage{cmbright}\Huge\$ from the left side. If you divide both sides by 14, you must divide every term by 14.