How do i finish this problem? i keep getting stumped here

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?

Graph y = -|x| + 2. click on the graph until the correct one appears.

Interpret the following expression (5y^2-7)^3/(2y)^2