Graph the quadratic function f(x)=-2x^2+6x-2

Last month, a 770 g box of cereal was sold at a grocery store for $3.10. however, this month, the cereal manufacturer launched the same cereal in a 640 g box, which is being sold at $2.50. what is the percent change in the unit price?

W-16=-12 solve each one step equation plz

Precalculus question, image attached.