Question

Each drink cost d dollars. Each snack cost s dollars. The Blake family buys 3 drinks and 2 snacks for $12. The reese family buys 2 drinks and 4 snacks for $16. What is the cost of one drink at the concession stand?

Answer 1

total cost for the blake family :

3d + 2s = 12 — (1)

total cost for the reese family :

2d + 4s = 16 — (2)

multiply equation 1 by 2 so that we can cancel out s later :

(1) x 2 : 2(3d+2s)=2(12)

6d+4s = 24 — (3)

using simultaneous equations,

(3) - (2)

(6d+4s) - (2d+4s) = 24-16

6d-2d+4s-4s = 8

4d = 8

d = 2

the cost of one drink is $2.

Answer 2

total cost for the blake family :
3d + 2s = 12 — (1)
total cost for the reese family :
2d + 4s = 16 — (2)

multiply equation 1 by 2 so that we can cancel out s later :
(1) x 2 : 2(3d+2s)=2(12)
6d+4s = 24 — (3)

using simultaneous equations,
(3) - (2)
(6d+4s) - (2d+4s) = 24-16
6d-2d+4s-4s = 8
4d = 8
d = 2

the cost of one drink is $2.