SOLUTION: Christi's mother gave her $9.00 to buy 10 cent and 15 cent stamps. Christi returned with $1.75 in change and a total of 60 stamps. How many of each kind of stamp did she buy?

Question 147686: Christi's mother gave her $9.00 to buy 10 cent and 15 cent stamps. Christi returned with $1.75 in change and a total of 60 stamps. How many of each kind of stamp did she buy?
Answer by mangopeeler07(462) (Show Source): You can put this solution on YOUR website!
-----With two variables: # of 10 cent stamps is x. # of 15 cent stamps is y. You have the prices of the stamps and the sum of the price of 60 stamps. So first set up an equation . Then set up . Then in the first equation solve for x. You should get . Plug that in the second equation and get . Distribute the ten and get . Combine like terms . Subtract 600 from both sides and get . Then divide by five and . Then plug in y in the original equation and get . So she bought 35 10cent stamps and 25 15 cent stamps.

-----With one variable: Also, you could start out with since you know the sum to be 60. Then distribute and get . Combine like terms and get . Subtract 900 from each side and get . Divide by -5 and get x=-35. Now, you can't buy a negative amount of stamps, so make 35 positive. . Then plug x into the original equation and get . So she bought 35 10cent stamps and 25 15 cent stamps.

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