SOLUTION: A stamp collection consists of 5,13, and 18 cent stamps. The number of 13 cent stamps is one less then twice the number of 5 cent stamps. The number of the 18 cent stamps is five

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Question 113438: A stamp collection consists of 5,13, and 18 cent stamps. The number of 13 cent stamps is one less then twice the number of 5 cent stamps. The number of the 18 cent stamps is five more then the number of 13 cent stamps. The total value of all the stamps is $2.60. Find the number of 13 cent stamps in the collections
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
F = number of 5c stamps
T = number of 13c stamps
E = number of 18c stamps
T+=+2F+-+1
E+=+T+%2B+5
5F+%2B+13T+%2B+18E+=+260
5F+%2B+13%282F+-+1%29+%2B+18E+=+260
5F+%2B+13%282F+-+1%29+%2B+18%28T+%2B+5%29+=+260
5F+%2B+13%282F+-+1%29+%2B+18%282F+-+1+%2B+5%29+=+260
5F+%2B+26F+-+13+%2B+36F+%2B+72+=+260
67F+%2B+59+=+260
67F+=+260+-+59
67F+=+201
F+=+3
T+=+2F+-+1
T+=+6+-+1
T+=+5
There are 5 thirteen cent stamps in the collection
check:
E+=+T+%2B+5
E+=+10
5F+%2B+13T+%2B+18E+=+260
5%2A3+%2B+13%2A5+%2B+18%2A10+=+260
15+%2B+65+%2B+180+=+260
260+=+260
OK