[ubuntu] How to delete an older version of Emacs?

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http://ubuntuforums.org – I installed Emacs 24.1 from source and compiled in the directory /usr/local/src. But after that I got Emacs 24.2 from ppa:cassou. Now I have two versions of Emacs and I want to get rid of the older ones. If have emacs and emacs-24.1 (both are the 24.1 version) in /usr/local/bin. And I also have emacs24-x (24.1 version) and emacs24 (24.2 version) in /usr/bin. I want to keep only the 24.2 version and I want to delete the others. But I don't want to mess things up. Also I click the emacs icon in the laucher it opens emacs 24.1. How do I change it to emacs 24.2? I know that there are many (Hardware)