Answer:
Steak sandwich = x = 4
Cheese fries = y = 1.75
Taco salad = z = 2
Step-by-step explanation:
Let :
Steak sandwich = x
Cheese fries = y
Taco salad = z
This week:
x + 2y + 2z = 11.50 - - - - (1)
Last week :
2x + 3y + z = 15.25 - - - (2)
Two weeks ago :
x + 4y + z = 13 - - - - - (3)
Taking (1) and (2)
x + 2y + 2z = 11.50 ___(1)
2x + 3y + z = 15.25 ___(2)
Multiply (1) by 2 and (2) by 1 and subtract
2x + 4y + 4z = 23
2x + 3y + z = 15.25
_______________
y + 3z = 7.75 - - - - (4)
Taking (2) and (3)
2x + 3y + z = 15.25 - - (2)
x + 4y + z = 13 - - - - - (3)
Multiply (2) by 1 and (3) by 2 and subtract
2x + 3y + z = 15.25
2x + 8y + 2z = 26
______________
-5y - z = - 10.75 - - - - - (5)
Lets solve (4) and (5)
y + 3z = 7.75 - - - - (4) - - - multiply by 5
-5y - z = - 10.75 - - - - - (5) - - - multiply by 1
Then add the result :
5y + 15z = 38.75
-5y - z = - 10.75
____________
14z = 28
z = 28 / 14
z = 2
To find y ; put z = 2 in (4)
y + 3z = 7.75
y + 3(2) = 7.75
y + 6 = 7.75
y = 7.75 - 6
y = 1.75
From equation 3 ;
x + 4y + z = 13 - - - - - (3)
x + 4(1.75) + 2 = 13
x + 7 + 2 = 13
x + 9 = 13
x = 13 - 9
x = 4
Hence,
Steak sandwich = x = 4
Cheese fries = y = 1.75
Taco salad = z = 2
