How many child tickets were sold that day?

Question

At the museum, child tickets cost $6.20, and Adult tickets cost $9.40. On sunday, three times as many adult tickets as child tickets were sold, for a total of $825.60. How many child tickets were sold that day?

Answer 1

6.2c + 9.4a -= 825.6, a = 3c

5.2c + 9.4(3c) = 5.2c + 28.2c = 33.4c = 825.6

c = 825.6/33.4 = about 24.71 = about 25 child tickets