When you eliminate variables for the first and second equations in the system, you should get a resulting statement of $\displaystyle{0}={0}\usepackage{cmbright}\Huge\$ . Likewise, when you eliminate variables for the second and third equations, you get the result of $\displaystyle{0}={0}\usepackage{cmbright}\Huge\$ . This indicates that there are an infinite number of solutions to this system.