This question is very similar to the cars problem as well, but instead of rates in mph, we have $/ticket.
Say the number of student tickets sold to be x. Thus the total income due to student tickets is ($3/ticket) x (x tickets) = 3x dollars
We know that 3000 tickets were sold, so whatever wasn't sold as a student ticket has to then be nonstudent ticket. Thus the total income due to nonstudent tickets is ($5/ticket) x (3000 - x tickets) = 5(3000-x) dollars
These together should make up the total income for the production.
* Remember, for word problems like these, the key is to put units on all the numbers that you're given. Working with the units will greatly help you in formulating the equations to solve for the unknown.