Multiply the second equation by $\displaystyle-{7}\usepackage{cmbright}\Huge\$ : $\displaystyle-{35}{x}+{21}{y}=-{14}\usepackage{cmbright}\Huge\$

Add this to $\displaystyle{35}{x}-{21}{y}={10}\usepackage{cmbright}\Huge\$ : $\displaystyle{0}=-{4}\usepackage{cmbright}\Huge\$

Since this is always false, no matter what values of x and y are used, there can be no solution to the equations.