If you solve a system and end up with the equations $\displaystyle{x}={0}\usepackage{cmbright}\Huge\$ and $\displaystyle{y}={2}\usepackage{cmbright}\Huge\$ , then the solution is $\displaystyle{\left({0},{2}\right)}\usepackage{cmbright}\Huge\$ . Here, if you substitute $\displaystyle{7}+{3}{y}\usepackage{cmbright}\Huge\$ for x in the second equation and then simplify, you will end up with the equation $\displaystyle{0}={2}\usepackage{cmbright}\Huge\$ . Since this is false, you cannot find numbers that make both equations true. The correct answer is that there is no solution.