You probably switched the values of x and y.

If you substitute these values correctly you get: $\displaystyle{2}{\left({0}\right)}-{7}{\left({10}\right)}={20}\usepackage{cmbright}\Huge\$

Simplify: $\displaystyle{0}-{70}={20}\usepackage{cmbright}\Huge\$ or $\displaystyle-{70}={20}\usepackage{cmbright}\Huge\$

This is not a true statement, so the ordered pair (0, 10) is not a solution to the equation.