Find the equation of the parabola that has zeros of x=-1 and x=3 and a y intercept of (0,-9)

Ngrid mixes 3.6 pounds of almonds with some raisins to make a trail mix. she divides the trail mix into 12 equal portions. each portion weighs 0.7 pound. how many pounds of raisins did she use to make the trail mix? express the answer to the nearest tenth.

A50% increase followed by 33 1/2% decrease

Having a hard time understanding this question (see attachment).