Multiply the first equation by $\displaystyle-{2}\usepackage{cmbright}\Huge\$ : $\displaystyle-{10}{x}-{28}{y}=-{22}\usepackage{cmbright}\Huge\$

Add this to $\displaystyle{10}{x}+{28}{y}={22}\usepackage{cmbright}\Huge\$ : $\displaystyle{0}={0}\usepackage{cmbright}\Huge\$

Since this is true regardless of the value x or y, there are an infinite number of solutions.