What am I missing

Question

A movie theater has a seating capacity of 285. The theater charges $5.00 for children, $7.00 for students, and $12.00 for adults. There are half as many adults as there are children. If the total ticket sales was $ 2058, How many children, students, and adults attended?

Answer 1

# of adults = N

# of children = 2N

# of students = 285 - 3N

( 12 x N ) + (5 x 2N) + (285 - 3N) x 7 = 2058

12N + 10N + 1995 - 21N = 2058

1995 + N = 2058

N = 2058 - 1995 => N = 63

So there are 63 adults, 126 children and 69 students in total .

Thanks

Mr.B