Need help! 8th grade math!! test due soon.:)

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?

Linda loans her friend $250 with a 5% monthly intrest rate. how much was the whole loan?

Annabelle's homework is 75% it took her three hours how long should she estimate it will take her to complete her homework.