Add the lengths and widths: $\displaystyle{\left({3}{a}+{5}\right)}+{\left({a}+{2}\right)}+{\left({3}{a}+{5}\right)}+{\left({a}+{2}\right)}\usepackage{cmbright}\Huge\$

Regroup using the commutative and associative properties: $\displaystyle{\left({3}{a}+{3}{a}+{a}+{a}\right)}+{\left({5}+{5}+{2}+{2}\right)}\usepackage{cmbright}\Huge\$

Combine like terms to simplify: $\displaystyle{8}{a}+{14}\usepackage{cmbright}\Huge\$