If you solve a system and end up with the equations $\displaystyle{x}={0}\usepackage{cmbright}\Huge\$ and $\displaystyle{y}={0}\usepackage{cmbright}\Huge\$ , then the solution is $\displaystyle{\left({0},{0}\right)}\usepackage{cmbright}\Huge\$ . For this system, you could have $\displaystyle{x}={0}\usepackage{cmbright}\Huge\$ , since $\displaystyle{0}={0}\usepackage{cmbright}\Huge\$ , but this does not mean that $\displaystyle{y}={0}\usepackage{cmbright}\Huge\$ . So the information does not tell you if $\displaystyle{\left({0},{0}\right)}\usepackage{cmbright}\Huge\$ is a solution of this system. The equation $\displaystyle{x}={x}\usepackage{cmbright}\Huge\$ does tell you that any value of x will work.