Correct. Multiply the coefficients of i together and remember that $\displaystyle{{i}}^{{2}}=-{1}\usepackage{cmbright}\Huge\$ .

$\displaystyle{\left(-{3}{i}\right)}{\left(-{15}{i}\right)}={\left(-{3}\right)}{\left(-{15}\right)}{\left({i}\right)}{\left({i}\right)}={\left({45}\right)}{\left({{i}}^{{2}}\right)}={\left({45}\right)}{\left(-{1}\right)}=-{45}\usepackage{cmbright}\Huge\$