Murray Universal breaker
The 20/30/30/20 (called a "quad" breaker) is created by coupling two tandem or "twin" breakers; a 20/30 and a 30/20.  In older panels twins will only fit in certain slots, because there were limits to the total number of circuits you could have in those panels. So only a few of the slots allowed the use of twins. On the directory sheet, usually glued to the inside of the door of the panel, there will be a difference in the way the breaker slots are shown, indicating which ones will accept twins. 



The slots that will accept twins will also accept full space breakers, but not the other way around. So one thing you can do is to check your directory to see which slots you can use and if they have full size breakers in them, move those to other slots and open up the slots that will accept the twins/quad.

If there are no slots left in your panel that allow twins, then you have to either replace the panel, or add a "sub panel".