Worded problem - finding and solving a system of linear equations.

Alright I'm sure I'm posting this in the right area if not I am truly sorry. So I have come across a problem that me and my brother have been trying to solve for a while and cannot figure it out would love some help. The problem is:

In a baseball stadium, there are three types of seats available. Box seats are $9, Reserved seats are $6, and lawn seats are $4. The stadium capacity is 3900. If all seats are sold, the total revenue to the club is $24,600. If one half of the box seats sold, one half of the reserved seats sold, and all the lawn seats are sold, the total revenue is $15,420. How many of each kind of seat are there?

I been trying for litterly 2 hours and I can't seem to figure it out. I've tryed making a System of linear equations in 3 variables and I can't figure it out. Any help would be awesome.

Thanks in advance guys!!