Factor $\displaystyle-{96}\usepackage{cmbright}\Huge\$ and $\displaystyle{{b}}^{{5}}\usepackage{cmbright}\Huge\$ to find perfect cubes: $\displaystyle{\sqrt[{{3}}]{{{\left(-{1}\right)}\cdot{8}\cdot{12}\cdot{{b}}^{{5}}}}}={\sqrt[{{3}}]{{{{\left(-{1}\right)}}^{{3}}\cdot{{2}}^{{3}}\cdot{12}\cdot{{b}}^{{3}}\cdot{{b}}^{{2}}}}}\usepackage{cmbright}\Huge\$

Separate the factors into individual radicals: $\displaystyle{\sqrt[{{3}}]{{{{\left(-{1}\right)}}^{{3}}}}}\cdot{\sqrt[{{3}}]{{{{2}}^{{3}}}}}\cdot{\sqrt[{{3}}]{{{12}}}}\cdot{\sqrt[{{3}}]{{{{b}}^{{3}}}}}\cdot{\sqrt[{{3}}]{{{{b}}^{{2}}}}}\usepackage{cmbright}\Huge\$

Simplify, using the property $\displaystyle{\sqrt[{{3}}]{{{{x}}^{{3}}}}}={x}\usepackage{cmbright}\Huge\$ : $\displaystyle-{1}\cdot{2}\cdot{\sqrt[{{3}}]{{{12}}}}\cdot{b}\cdot{\sqrt[{{3}}]{{{{b}}^{{2}}}}}=-{2}{b}{\sqrt[{{3}}]{{{12}{{b}}^{{2}}}}}\usepackage{cmbright}\Huge\$