My math teacher gave us this problem, and didnt really expalin how to do it..If someone would be so kind as to show me what to do, I would appriciate it.

Baseball tickets for a grade school game sell for $5 for adults and $2 for students. $900 was made in ticket sales for one game, and the total amount of tickets sold was 270. How many of each type where sold?

Thanks in advance.