Explanation:
adult = x
student = y
The auditorium can hold up to 500 people (student and adult)
x + y ≤ 500
Their goal is to raise at least 50.000
10x + 8y ≥ 50.000 or
5x + 4y ≥ 25000
(i think it's impossible to reach this only from ticket)
so the inequalities work in this case is
x + y ≤ 500
5x + 4y ≥ 25000
x > 0
y > 0