Question

Three families bought food at the baseball game. The Smith family spent $16.50 on 3 hot dogs, 2 sodas, and 1 candy bar. The Patterson family spent $26 on 4 hot dogs, 4 sodas, and 2 candy bars. The Nguyen family spent $13.75 on 2 hot dogs, 1 soda, and 3 candy bars. Which of the following systems of equations could be used to determine the price of each item?

Answer 1

Explanation:

Let

Price of

Hotdogs = x

Sodas = y

Candy bar = z

Smith family

Hotdogs = 3

Sodas = 2

Candy bar = 1

Total cost = $16.50

3x + 2y + z = 16.50

Patterson family

Hotdogs = 4

Sodas = 4

Candy bar = 2

Total = $26

4x + 4y + 2z = 26

Nguyen family

Hotdogs = 2

Sodas = 1

Candy bar = 3

Total cost = $13.75

2x + y + 3z = 13.75

The equations

3x + 2y + z = 16.50 (1)

4x + 4y + 2z = 26 (2)

2x + y + 3z = 13.75 (3)

Multiply (1) by -2

-2(3x + 2y + z = 16.50)

-6x - 4y - 2z = -33

-6x - 4y - 2z = -33 (1a)

4x + 4y + 2z = 26 (2)

Add (1a) and (2)

-6x + 4x = -33 + 26

- 2x = -7

x = -7/-2

= 3.5

x = $3.5

Multiply (3) by -4

-4(2x + y + 3z = 13.75) (3)

-8x - 4y - 12z = -55 (3a)

Add (3a) and (2)

-8x - 4y - 12z = -55 (3a)

4x + 4y + 2z = 26 (2)

-8x + 4x -12z + 2z = -55 + 36

-4x - 10z = -29

Substitute the value of x into

-4x - 10z = -29

-4(3.5) - 10z = -29

-14 - 10z = -29

-10z = -29 + 14

-10z = - 15

z = -15 / - 10

= 1.5

z = $1.5

Substitute values of x and z into (1)

3x + 2y + z = 16.50

3(3.5) + 2y + 1.5 = 16.50

10.5 + 2y + 1.5 = 16.50

12 + 2y = 16.50

2y = 16.50 - 12

2y = 4.50

y = 4.50 / 2

y = $2.25