Amachine made 3 1/2 pencils in 1/6 of a minute. it made pencils at a rate of how many per minute?

What is the expression in factored form? 3x^2 + 18x + 24 a. 3(x+2)(x+4) b. 3(x-2)(x+4) c. 3(x-2)(x-4) d. 3(x+2)(x-4)