Question

At a restaurant, three salads, two sandwiches, and one drink cost $17.75. One salad, one sandwich, and three drinks cost $10.75. A salad costs twice as much as a drink. How much does each item cost?

Answer 1

A salad costs $2.50

A sandwich costs $4.50

A drink costs $1.25

Explanation:

Let x represent the salad, y represent the sandwich, and z represent the drink.

Since three salads, two sandwiches, and one drink cost $17.75:

3x + 2y + z = 17.75 (1)

Since one salad, one sandwich, and three drinks cost $10.75:

x + y + 3z = 10.75 (2)

Since a salad costs twice as much as a drink:

x = 2z (3)

Multiply the equation 2 by -2 then, sum the equation 1 and equation 2:

-2x - 2y - 6z = -21.50

3x + 2y + z = 17.75

→ x - 5z = -3.75

Replace the x with 2z using equation 3:

2z - 5z = -3.75

-3z = -3.75

z = 1.25

x = 2z → x = 2.50

x + y + 3z = 10.75 → 2.50 + y + 3.75 = 10.75 → y + 6.25 = 10.75 → y = 4.50