Doing this will result in two equations with the term $\displaystyle{18}{x}\usepackage{cmbright}\Huge\$ . This could be helpful, but because you really need to get opposite variable terms in the two equations, you will then have to multiply one equation by $\displaystyle-{1}\usepackage{cmbright}\Huge\$ . This will be a total of three multiplications performed. However, it is possible to produce opposite variable terms with just one multiplication.