Answer: 50
Explanation:
Let x represent student tickets and y represent adult tickets.
x + y = 300
5x + 11y = 3000
Just use substitution to remove one variable. Let's remove x as it would be easiest.
5x + 5y = 1500
5x + 11y = 3000
------------------------
-6y = -1500
y = 250
Then x would equal 50, since 250 + x = 300.