To solve this question let's represent our situation by an expression.
If we consider "x" as the value for tickets at the event, so "x-2" represent the value for pre-sale tickets. And once we have the number of each tickets (54 units for pre-sale and 82 units for tickets at the event) we have sold and also the amount the group raised ($980), now we can create our expression and find "x":
Now we have:
Tickets at the event : x = $8
Pre-sale: x-2 = 8-2 = $6
And those are the final answers.