How can simple interest to make saving money easy

What kind of bond pays interest which is exempt from tax?

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 the discriminant if a quadratic equation is 4 which statement describes the roots?