If your ubuntu installation started throwing errors like unmet dependencies while installing packages then let me show you how to solve that , solve using these two methods
some packages could not be installed. This may mean that you have requested an impossible situation or if you are using the unstable distribution that some required packages have not yet been created or been moved out of Incoming. The following information may help to resolve the situation: The following packages have unmet dependencies: package1 : Depends: package2 (>= 1.8) but 1.7.5-1ubuntu1 is to be installed E: Unable to correct problems, you have held broken packages.
first : open software center and it will pop up for repairing catalog
second : open terminal
sudo apt-get clean sudo apt-get -f install sudo apt-get update
if problem still persist then remove recently added custom repositories