$\left( 3{x}^{2}+15x-x-5 \right) \times \left( 4x-3 \right)$
Collect like terms$\left( 3{x}^{2}+14x-5 \right) \times \left( 4x-3 \right)$
Simplify the expression$12{x}^{3}-9{x}^{2}+56{x}^{2}-42x-20x+15$
Collect like terms$12{x}^{3}+47{x}^{2}-42x-20x+15$
Collect like terms$12{x}^{3}+47{x}^{2}-62x+15$