SOLUTION: Mary has a $90 gift certificate for a book store where paperbacks cost $9 and hardback books cost $12. She must spend at least $25 and no more than $90 to use the gift certificate

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Question 128751: Mary has a $90 gift certificate for a book store where paperbacks cost $9 and hardback books cost $12. She must spend at least $25 and no more than $90 to use the gift certificate. Write a system of inequalities to determine the formula for using the gift certificate.
I came up with 9x + 12y is less than or equal to 90; and 9x + 12y is greater than or equal to 25. Is that correct?
Answer by checkley71(8403) About Me  (Show Source):
You can put this solution on YOUR website!
25<=9X+12Y<=90 THIS IS A SINGLE EQUATION FOR THIS PROBLEM.