A cellular phone service company charges 20 cents for each minute or part of a minute of airtime. If the total charge y in cents is a function of the number of minutes x that Cora uses her phone, what is the range of this function?

The library sells 376 books at its annual used-book sale. the sale takes in a total of $2119. children's books cost $4, and adult books cost $7. let x = number of children's books sold, and let y = the number of adult books sold. which system of equations can the librarians use to model this situation?