Checking your Ubuntu Version
Enter the command lsb_release -a
Your version will be shown on the Description.
In the Terminal
txxx@xxxxxxx:~$ lsb_release -a
LSB Version: core-2.0-amd64:core-2.0-noarch:core-3.0-amd64:core-3.0-noarch:core-3.1-amd64:core-3.1-noarch:core-3.2-amd64:core-3.2-noarch:core-4.0-amd64:core-4.0-noarch
Distributor ID: Ubuntu
Description: Ubuntu 13.04
Release: 13.04
Codename: raring
If there are no lsb modules installed in your machine, you get No LSB modules are available.
You can install the lsb modules using the command.
sudo apt-get install lsb-core