Someone help me with other problem

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?

George writes the mixed number as sum and uses the distributive property 1/2.-2/5=1/2-2+2/5=1/2

Which of the following statements would be sufficient to prove that parallelograms pqrs is a rectangle ?