310 advance tickets were sold and 340 at the door tickets were sold.
Step-by-step explanation:
You know that thirty more tickets were sold at the door than in advance so we can find out how much that costs first.
More tickets sold = 30 × $5
= $150
Remaining tickets = $2630 - $150
= $2480
Now that you have deducted the extra tickets, $2480 is the sum of the tickets where the number of advance and at the door tickets are the same. You could find how much one "set" costs before finding the number of sets there are.