Can't fix the resolution on virtualbox using guest additions

I started using Ubuntu not to long ago because I wanted to give it a try. Soon I got annoyed by the low resolution on virtualbox.

I was told to install 3 packages using the following terminal script:

    sudo apt-get install virtualbox-guest-dkms virtualbox-guest-utils virtualbox-guest-x11

However, once I enter my password and the script loads, I get this message:

   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:
virtualbox-guest-x11 : Depends: xorg-video-abi-15
                    Depends: xserver-xorg-core (>= 2:1.14.99.902)
E: Unable to correct problems, you have held broken packages.

what does this mean? How can I fix it?

On the host OS go to the menu and select to install it from there. It will load a cd inside the virtualized OS and inside the cd there will be a zip package. Copy it to the desktop and extract it.

Then open the terminal and move to the desktop and execute with ./ command the .sh file in the extracted folder from the zip. Follow the instructions to install it (very easy) and you will have it working perfectly!