Correct. $\displaystyle-{9}{{x}}^{{3}}\usepackage{cmbright}\Huge\$ must be distributed to all the terms in the parentheses. $\displaystyle-{9}{{x}}^{{3}}{\left({2}{{x}}^{{3}}-{7}{{x}}^{{2}}{y}+{4}{{y}}^{{2}}\right)}=-{9}{{x}}^{{3}}{\left({2}{{x}}^{{3}}\right)}-{\left(-{9}{{x}}^{{3}}\right)}{\left({7}{{x}}^{{2}}{y}\right)}+{\left(-{9}{{x}}^{{3}}\right)}{\left({4}{{y}}^{{2}}\right)}=\usepackage{cmbright}\Huge\$ $\displaystyle-{18}{{x}}^{{6}}+{63}{{x}}^{{5}}{y}-{36}{{x}}^{{3}}{{y}}^{{2}}\usepackage{cmbright}\Huge\$ .