Ubuntu Server 12.04: E: Unable to correct problems, you have held broken packages

So I have to install Ubuntu Server 12.04 as part of my industrial training, but I ran into some problems while trying to use apt-get.

Namely, whenever I try to install any new software, it will either result in this:

http://i.imgur.com/gFECQ8X.jpg

or

http://i.imgur.com/MzHzWUL.jpg

and I've edited the /etc/apt/sources.list in vi, so now it looks like this:

http://i.imgur.com/JOeOzXc.jpg
http://i.imgur.com/Z6jgAuK.jpg
http://i.imgur.com/pXfeRWX.jpg

(The changes I've made are for the last four entries.)

I've tried fixing it using apt-get update and upgrade will usually result in this:

http://i.imgur.com/sGcW3uB.jpg

And when I tried using aptitude, this will usually happen:

http://i.imgur.com/Utl2hU5.jpg

I've also tried:

sudo apt-get autoclean $$ apt-get clear cache

Which resulted in:

http://i.imgur.com/hT4ZBWI.jpg

So I think the apt-get component of this install is broken. Any advice on how to fix this?

Common problem.. it's seems either you are purposefully 'holding' certain packages from being install (or their version being changed..)..or.

You need to update your repositories.. either normally (with the update command).. or, you need to add/delete the repositories, that are conflicting with your request.

You could also alter your request, if possible (obvious.. i no..).

Aptitude is awesome, but you have to baby it alot, to get what you want. Actually, sometimes apt-get is good to get something installed (when aptitude won't).. but be careful when it does.. because sometimes it breaks things... (so make sure your backups are cool..) and reboot a couple of times to ensure everything is grand.