Find each individual product and combine the like terms:

$\displaystyle{x}{\left({{x}}^{{2}}\right)}+{x}{\left({2}{x}\right)}+{x}{\left({4}\right)}+{7}{\left({{x}}^{{2}}\right)}+{7}{\left({2}{x}\right)}+{7}{\left({4}\right)}\usepackage{cmbright}\Huge\$

$\displaystyle={{x}}^{{3}}+{2}{{x}}^{{2}}+{4}{x}+{7}{{x}}^{{2}}+{14}{x}+{28}={{x}}^{{3}}+{9}{{x}}^{{2}}+{18}{x}+{28}\usepackage{cmbright}\Huge\$