is a number that can be used to describe a part of whole a part of a set a location on a number line or a divison

How do you solve a question like this?

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?

If jklm is a trapezoid, which statements must be true?