If you multiply the first equation by $\displaystyle-{4}\usepackage{cmbright}\Huge\$ and add it to the second equation, the resulting statement is $\displaystyle{0}={0}\usepackage{cmbright}\Huge\$ . Multiply the third equation by 4 and add it to the second equation. The resulting statement is also $\displaystyle{0}={0}\usepackage{cmbright}\Huge\$ . This means that the system has an infinite number of solutions.