Since $\displaystyle{x}=-{5}\usepackage{cmbright}\Huge\$ ,

$\displaystyle{3}{{x}}^{{2}}-{6}{x}+{9}={3}{{\left(-{5}\right)}}^{{2}}-{6}{\left(-{5}\right)}+{9}={3}{\left({25}\right)}-{6}{\left(-{5}\right)}+{9}={75}+{30}+{9}={114}\usepackage{cmbright}\Huge\$ .