You may have incorrectly substituted into one of the equations, as the ordered pair is a solution to the first equation. Substitute 5 in for x and 4 in for y, and then be careful simplifying. The correct answer is: $\displaystyle{\left({5},{4}\right)}\usepackage{cmbright}\Huge\$ is a solution to one equation but not the other one, so it is not a solution to the system.