Change the subtraction to adding the opposite: $\displaystyle{\left(-{6}{{g}}^{{2}}+{11}{g{-}}{3}\right)}+{\left(-{4}{g{+}}{7}\right)}\usepackage{cmbright}\Huge\$

Regroup to match like terms: $\displaystyle-{6}{{g}}^{{2}}+{\left({11}{g{+}}-{4}{g}\right)}+{\left(-{3}+{7}\right)}\usepackage{cmbright}\Huge\$

Combine like terms: $\displaystyle-{6}{{g}}^{{2}}+{7}{g{+}}{4}\usepackage{cmbright}\Huge\$