(x+3)(x+4)(x+5)

just need help with the steps to solve it

(x+3)(x+4)(x+5) , keep the first factor for a while

= (x+3)(x^2 + 9x + 20) , now use the first one
= x^3 + 9x^2 + 20x + 3x^2 + 27x + 60
= x^3 + 12x^2 + 47x + 60