Answer:
lemonade = 11
Explanation:
let p = pink lemonade
let t = sweet tea
create a system of equations -- one with quantity, one with associate costs
p + t = 21
2.5p + 4t = 67.5
substitution method: let t = 21 - p
2.5p + 4(21 - p) = 67.5
2.5p + 84 - 4p = 67.5
-1.5 p = -16.5
p = 11
t = 21 - 11
t = 10