Question

Johnny's cafe serves desserts. One serving of ice cream and two servings of blueberry pie provides 800 calories. Three servings of ice cream and two servings of blueberry pie provides 1200 calories. Find the caloric content of each item.

Answer 1

1 i + 2 b = 800
3 i + 2 b = 1200
-------------------- subtract
-2 i = - 400
i = 200
200 + 2 b = 800
b = 300

Answer 2

ice cream calories ---- x
pie calories ---- y

x + 2y = 800 -----> x = 800-2y
3x + 2y = 1200
substitute:
3(800-2y) + 2y = 1200
2400 - 6y + 2y = 1200
-4y = -1200
y = 300
then x = 800-2(300) = 200