Some beginner's help please?

I have this query I've been trying to write all week and had no success. Here's the problem.

In table "A" I list a TRBLTKT number, CREATEDBY number and CLOSEDBY number. The Createdby and Closedby numbers join over to another table called PERSONAL, that has IDNUM, LASTNAME and FIRSTNAME as fields. My problem is, how do I write a select that resolves the Createdby and closedby numbers seperately (if they were different people). For one, I'd do:
select a.trbltkt, personal.lastname from a, personal where a.createdby = personal.idnum;

how do I write it to match both fields.. I'm stumped.. help please...

                             Randy