SOLUTION: Another word problem...help! Allen bought 30 stamps at the post office in 39 cent and 24 cent denominations. If the total cost of the stamps was $9.90, how many 39 cent stamps d

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Question 53269: Another word problem...help!
Allen bought 30 stamps at the post office in 39 cent and 24 cent denominations. If the total cost of the stamps was $9.90, how many 39 cent stamps did Allen buy?
Answer by Nate(3500) About Me  (Show Source):
You can put this solution on YOUR website!
number of 39 cent stamps = x
number of 24 cent stamps = y
y+%2B+x+=+30 which can look like: y+=+30+-+x
and
0.39x+%2B+0.24y+=+9.9
0.39x+%2B+0.24%2830+-+x%29+=+9.9
0.39x+%2B+7.2+-+0.24x+=+9.9
0.15x+=+2.7
x+=+18
plug:
y+=+30+-+x
y+=+30+-+18+=+12
There are 18 0.39 cent stamps and 12 0.24 cent stamps.