math
posted by tiff .
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.

let s3 s8, and s15 represent the 3 cent, 8cent and 15 cent stamps
now translate the English into math
<The number of 8 cent stamps is one less than triple the number of 3 cent stamps> > s8 = 3s3  1
<The number of 15 cent stamps is six less than the number of 8 cent stamps> > s15 = s8  6 = 3s37
Now form an equation using the value of the stamps
3(3s) + 8(3s3  1) + 15(3s3  7) = 247 and solve