A movie theater sold 800 tickets and made $4400 in one night. If an adult ticket costs $8 and a children's ticket costs $4, how many adult tickets were sold?

Let x = adult tickets

Let y = children's tickets

x + y = 800

8x + 4y = 4,400

From the first eq, x = 800 - y, plug this in to the second eq

8 (800-y) + 4y = 4,400

6400 - 8y + 4y = 4,400

2000 = 4y

500 = y

x = 800 - 500

x = 300

300 adult tickets were sold.