Question

the cost of five posters and three flags is $137.25. the cost of three posters and four flags is $122.50. what is the cost of one poster?

Answer 1

5p + 3f = 137.25 | x 3

3p + 4f = 122.50 | x 5

15p + 9f = 411.75

15p + 20f = 612.50

15p + 20f - 15p - 9f = 612.50 - 411.75

20f - 9f = 200.75

11f = 200.75

f = $18.25

3p + 4(18.25) = 122.50

3p = 122.50 - 73

3p = 49.50

p = $16.50

Answer 2

$16.50

Explanation:

let cost of poster be p and cost of flag be f, then

5p + 3f = 137.25 → (1)

3p + 4f = 122.5 → (2)

Multiplying (1) by 4 and (2) by - 3 and adding will eliminate f

20p + 12f = 549 → (3)

- 9p - 12f = - 367.5 → (4)

Add (3) and (4) term by term

11p = 181.5 ( divide both sides by 11 )

p = 16.5

Thus the cost of 1 poster is $16.50