sudo apt-get install gnome-shell gnome-shell-extensions
Reading package lists... Done
Building dependency tree
Reading state information... Done
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:
 gnome-shell : Depends: gnome-session but it is not going to be installed
               Depends: gnome-settings-daemon (>= 3.16.0) but it is not going to be installed
               Depends: gnome-shell-common (= 3.18.4-0ubuntu3) but 3.18.5-0ubuntu0.1 is to be installed
               Recommends: gnome-control-center but it is not going to be installed
               Recommends: gdm3 (>= 3.10.0.1-3~) but it is not going to be installed
 gnome-shell-extensions : Depends: gnome-session (>= 3.8) but it is not going to be installed
                          Recommends: gnome-tweak-tool (>= 3.18) but it is not going to be installed
E: Unable to correct problems, you have held broken packages.