Iam lost i need to know the steps on solving 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?

Solving algebraic equations 2m+3=11

Amachine part consists of a half sphere and a cylinder, as shown in the figure. the total volume of the part is π cubic inches.