Last year, my parents had a combined income of $50,000. they paid $13,000 in federal income taxes. what fraction shows how much my parents spent on their federal taxes?

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?