Factor out the GCF in $\displaystyle{18}{{a}}^{{4}}{{b}}^{{2}}+{30}{{a}}^{{2}}{{b}}^{{3}}\usepackage{cmbright}\Huge\$ . Then supply the missing exponent.

$\displaystyle{18}{{a}}^{{4}}{{b}}^{{2}}+{30}{{a}}^{{2}}{{b}}^{{3}}={6}{{a}}^{?}{{b}}^{{2}}{\left({3}{{a}}^{{2}}+{5}{b}\right)}\usepackage{cmbright}\Huge\$