Let the price of a student ticket be t. That makes the price of an adult ticket t + 3, as adult tickets are three more dollars than student tickets. Now we have:
student ticket = t adult ticket = t + 3
To model the scenario that Mr. Williams bought 7 student tickets and 6 adult tickets, set the sum of the products of those numbers and the ticket costs equal to 83 (the cost of all tickets combined) and solve algebraically for t.
