x=24+12

x=36

a) \(3x^2+10x+3=3x^2+9x+x+3\)

\(=3x\left(x+3\right)+\left(x+3\right)\)

\(=\left(x+3\right)\left(3x+1\right)\)

b)\(5x^2+14x-3=5x^2+15x-x-3\)

\(=5x\left(x+3\right)-\left(x+3\right)\)

\(=\left(5x-1\right)\left(x+3\right)\)

c)\(6x^2+7x-3=6x^2+9x-2x-3\)

\(=3x\left(2x+3\right)-\left(2x+3\right)\)

\(=\left(3x-1\right)\left(2x+3\right)\)