A concession stand sold a total of 138 small and large popcorns. A small popcorn costs $2.50, and a large popcorn costs $4.00. Total popcorn sales were $466.50. How many large popcorns were sold?

X = small popcorns

y = large popcorns

x+y=138

2.50x + 4.00y = 466.50

y = 138-x

2.50x + 4.00 (138-x) = 466.50

2.50x + 552-4x = 466.50

2.50x-4x = 466.50 - 552

-1.5x = - 85.5

-1.5x/-1.5 = - 85.5/-1.5

x = 57

Since,

x+y=138

(57) + y = 138

y = 138 - 57

y = 81

Therefore 81 large popcorns were sold!