Algebra - Text equations again! Can't start this one at all!?

Question

A stamp collection consist of 3 cents, 8 cents, and 13 cents stamps. The number of 8 cent stamps is three less than twice the number of 3 cents stamps. The number of 13 cents stamps is twice the number of 8 cent stamps. The total value of all the stamps is 2.53. find the number of 3 cent stamps in the collection.

PLEASE HELP!

Answer 1

Number 3 cent stamps = n
Number 8 cent stamps = 2n-3
number 13 cent stamps = 2(2n-3)

3n + 8(2n-3) + 13*2(2n-3) = 253

3n + 16n - 24 + 52n - 78 = 253

71n - 102 = 253

71n = 355

n = 5

5 3 cent stamps

Answer 2

let x = number of 3 cent stamps
y = number of 8 cent stamps
z = number of 13 cent stamps

The number of y is 3 less than twice the number of x
y+3 = 2x ----------------> y = 2x - 3

The number of 13 cent stamps is twice the number of 8 cent st.
z = 2y --------------> z = 2(2x - 3) = 4x - 6

3*x + 8*y +13*z = 2.53, now substitue the above

3x + 8(2x -3) + 13(4x-6) = 2.53
(3+16+ 52)x +(-24 - 78) = 2.53
71x= 3.55 means that x= 5
y =2x - 3 = 7
z = 4x -6 = 20 - 6 = 14
please double check for errors

Answer 3

.03a + .08b + .13c = 2.53
3a + 8b + 13c = 253

b = 2a - 3
c = 2b

c = 2(2a - 3)
c = 4a - 6

3a + 8(2a - 3) + 13(4a - 6) = 253
3a + 16a - 24 + 52a - 78 = 253
71a - 102 = 253
71a = 355
a = 5

b = 2(5) - 3 = 10 - 3 = 7
c = 4(5) - 6 = 20 - 6 = 14

5 : 3 cent stamps
7 : 8 cent stamps
14 : 13 cent stamps

ANS : 5