SOLUTION: Cindy has 40 coins, consisting of dimes and quarters, that total $6.85. How many coins of each kind does she have? How do I set up this problem to solve it? thank you!

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Question 745278: Cindy has 40 coins, consisting of dimes and quarters, that total $6.85. How many coins of each kind does she have?
How do I set up this problem to solve it?
thank you!
Answer by savvyhush23(50) About Me  (Show Source):
You can put this solution on YOUR website!
1 Dime = $0.10 and 1 Quarter = $0.25
Let x - the number of dime
y - the number of quarter
Number of coins she has: x + y = 40 coins
Now, 0.10x for dime plus 0.25y for quarter is equal to $6.85 that is,
0.10x+0.25y=6.85
Then,
Multiply -0.10 to (x + y = 40) it becomes -0.10x -0.10y = -4, then add this to
0.10x+0.25y=6.85 it yields y = 19 quarters and x = 21 dimes