Question

A costumer walked into a restaurant and purchased 4 chicken sandwiches and 5 large sodas for $22.50. The customer behind him bought 7 chicken sandwiches and 6 large sodas for $35.25. How much does a chicken sandwich cost and how much is a large soda?

Answer 1

Answer: the cost of a chicken sandwich is $3.75

the cost of a large soda is $1.5

Explanation:

Let x represent the cost of a chicken sandwich.

Let y represent the cost of a large soda.

A costumer walked into a restaurant and purchased 4 chicken sandwiches and 5 large sodas for $22.50. This means that

4x + 5y = 22.5 - - - - - - - -1

The customer behind him bought 7 chicken sandwiches and 6 large sodas for $35.25. This means that

7x + 6y = 35.25 - - - - - - - - - -2

Multiplying equation 1 by 7 and equation 2 by 4, it becomes

28x + 35y = 157.5

28x + 24y = 141

Subtracting

11y = 16.5

y = 16.5/11 = 1.5

Substituting y = 1.5 into equation 1, it becomes

4x + 5 × 1.5 = 22.5

4x + 7.5 = 22.5

4x = 22.5 - 7.5 = 15

x = 15/4 = 3.75

Answer 2

Set up an equation for each customer:

4C + 5S = 22.50

7C + 6S = 35.25

Multipyy the first equation by -1.75 to make the 4C the inverse of 7c:

4C + 5S = 22.50 x -1.75 = -7C - 8.75S = -39.375

Now add the two equations to eliminate the C variable:

7C +6S = 35.25 + -7C - 8.75S = -39.375

= -2.75S = -4.125

Divide both sides by -2.75 to solve for S:

S = -4.125 / -2.75

S = 1.50

The price of a soda is $1.50

Now replace S in an equation with 1.50 and solve for C:

4C + 5(1.50) = 22.50

Simplify:

4C + 7.50 = 22.50

Subtract 7.50 from both sides:

4C = 15

Divide both sides by 4:

C = 15/4

C = 3.75

The sandwich costs $3.75

Soda = $1.50

Sandwich = $3.75