SOLUTION: Please help with this problem. I have tried to look at other similar problems to help guide me, but is not working. --> A stamp collection consists of 3, 8, and 15 cent stamps. T

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Question 161980: Please help with this problem. I have tried to look at other similar problems to help guide me, but is not working.
--> A stamp collection consists of 3, 8, and 15 cent stamps. The number of 8 cent stamps is one less than triple the number of 3 cent stamps. The number of 15 cent stamps is six less than the number of 8 cent stamps. The total value of all the stamps is $2.47. Find the number of 8 cent stamps in the collection. [Fifteen points for the correct algebra equation and five points for solving the equation.
Answer by vleith(2983) About Me  (Show Source):
You can put this solution on YOUR website!
Let t be the three cents stamps, e be the 8 cents ones and f be the fifteens
Given e+=+3t-1
f+=+e+-6 so e+=+f%2B6
which says 3t-1+=+f+%2B+6
so 3t+-+7+=+f
247+=+3t+%2B+8e+%2B+15f
Now using the values for f and e in terms of t above, substitute and solve
247+=+3t+%2B+8%283t-1%29+%2B+15%283t+-7%29
247+=+3t+%2B+24t+-8+%2B+45t+-+105
360+=+72t+
5+=+t
Now use this value for t to find f and e