Incorrect. Set up the subtraction:

$\displaystyle{g{{\left({x}\right)}}}-{f{{\left({x}\right)}}}={6}{{x}}^{{2}}-{3}{x}+{7}-{\left({6}{{x}}^{{2}}-{5}{x}+{7}\right)}\usepackage{cmbright}\Huge\$

Distribute the minus sign to all the terms of $\displaystyle{f{{\left({x}\right)}}}\usepackage{cmbright}\Huge\$ and then combine like terms. The correct answer is $\displaystyle{2}{x}\usepackage{cmbright}\Huge\$ .