You may have ignored the negative sign in front of the y-coordinate. This ordered pair is not a solution to the equation $\displaystyle{x}+{y}={5}\usepackage{cmbright}\Huge\$ because $\displaystyle{\left({0}\right)}+{\left(-{5}\right)}={5}\usepackage{cmbright}\Huge\$ , or $\displaystyle-{5}={5}\usepackage{cmbright}\Huge\$ , is not a true statement.