Can someone me with the equation part of this question?

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.

83 = 7t + 6(t + 3)
83 = 7t + 6t + 18
83 = 13t + 18
65 = 13t
5 = t

Remember, t represents the cost of one student ticket, thus one student ticket costs 5 dollars, and one adult ticket costs 5 + 3 dollars or 8 dollars.

The price of one adult ticket is $8.