$\displaystyle{6}{x}{{y}}^{{2}}\usepackage{cmbright}\Huge\$ is the greatest common factor of $\displaystyle{18}{{x}}^{{3}}{{y}}^{{2}}\usepackage{cmbright}\Huge\$ , $\displaystyle{30}{{x}}^{{2}}{{y}}^{{4}}\usepackage{cmbright}\Huge\$ , and $\displaystyle{42}{x}{{y}}^{{3}}\usepackage{cmbright}\Huge\$ .