SOLUTION: A music store is selling compact disks for $11.50 and $7.50. You buy 12 disks and spend a total of $110. How many compact disks that cost $11.50 did you buy?

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Question 388392: A music store is selling compact disks for $11.50 and $7.50. You buy
12 disks and spend a total of $110. How many compact disks that cost
$11.50 did you buy?
Answer by Fombitz(32388) About Me  (Show Source):
You can put this solution on YOUR website!
Let A be the number of $11.50 disks, B the number of $7.50 disks,
1.A%2BB=12
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1150A%2B750B=11000
2.23A%2B15B=220
Multiply eq. 1 by (-15) and add to eq. 2,
-15A-15B%2B23A%2B15B=-180%2B220
8A=40
highlight%28A=5%29
Then from eq. 1,
5%2BB=12
highlight%28B=7%29
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