A concession stand sells two sizes of popcorn. The small bag holds 20 ounces and costs $4, and the large bag holds 32 ounces and sells for $6. The concession stand sold 200 bags of popcorn and made $900 from the sale of popcorn.

X = large bag of popcorn

y = small bag of popcorn

x + y = 200 ... x = 200 - y

4x + 6y = 900

4 (200 - y) + 6y = 900

800 - 4y + 6y = 900

-4y + 6y = 900 - 800

2y = 100

y = 50 < = = = large bags sold

x + y = 200

x + 50 = 200

x = 200 - 50

x = 150 < = = small bags