Correct. Multiply each term in the first polynomial with each term in the second polynomial and then combine the like terms.

$\displaystyle{2}{n}{\left({5}{{n}}^{{2}}\right)}+{2}{n}{\left({3}{n}\right)}+{2}{n}{\left(-{4}\right)}+{5}{\left({5}{{n}}^{{2}}\right)}+{5}{\left({3}{n}\right)}+{5}{\left(-{4}\right)}\usepackage{cmbright}\Huge\$

$\displaystyle={10}{{n}}^{{3}}+{6}{{n}}^{{2}}-{8}{n}+{25}{{n}}^{{2}}+{15}{n}-{20}={10}{{n}}^{{3}}+{31}{{n}}^{{2}}+{7}{n}-{20}\usepackage{cmbright}\Huge\$