Asked by Steve

A stamp collection consists of 3¢, 12¢, and 15¢ stamps. The number of 3¢ stamps is three times the number of 12¢ stamps. The number of 15¢ stamps is three less than the number of 12¢ stamps. The total value of the stamps in the collection is $2.43. Find the number of 15¢ stamps in the collection.

Please, Im really struggling with these types of problems.
Answered by Steve
If someone could just show me how to set up a formula that would be great!
Answered by Damon
3 cent = x
12 = y
15 = z

x = 3 y
z +3 = y

3 x + 12 y + 15 z = 243

3 (3y) + 12 y + 15 (y-3) = 243

get it ?
Answered by Steve
so it would then turn into 9y+12y+15y-45=243
36y-45=243 ( add the y's together)
36y = 288 (add 45 to 243)
y = 8? (288 divided by 36)
Answered by Damon
yes, y is 8 but it asked for z

z = y-3 = 5
Answered by Steve
OHH! Thank you very much, that would have been a pretty frustrating error if I continued without noticing! Thank you, Damon. Have a great night!
Answered by Damon
You are welcome.
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