$\displaystyle{6}{{x}}^{{2}}{{y}}^{{3}}{{z}}^{{4}}{\left({3}-{5}{x}\right)}={18}{{x}}^{{2}}{{y}}^{{3}}{{z}}^{{4}}-{30}{{x}}^{{3}}{{y}}^{{3}}{{z}}^{{4}}\ne{18}{{x}}^{{2}}{{y}}^{{3}}-{30}{{x}}^{{3}}{{z}}^{{4}}\usepackage{cmbright}\Huge\$ so this answer is incorrect.