If total cost of the room (or rooms) for 6 students is $2000 and $20 buys them each a meal and each has a free chaperone, then the cost is $(2000+6*20)=$2120. If each student has one ticket, then the cost of each ticket is 2120/6=1060/3=$353.33, covering the room and meal cost.
If the total cost of the room(s) is $2000 for all x students then the cost for one student is 2000/x. Add to this the cost of one meal at $20, and the total cost for the room and the ticket cost will be 2000/x+20.