Installing Mate 1.8 for Ubuntu 15.04 Vivid
How to Install Mate 1.8 desktop on Ubuntu 15.04 Vivid Vervet i386/amd64 GNU+Linux.
The MATE desktop Environment is the continuation of GNOME 2. It provides an intuitive and attractive desktop environment.

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Open a Command Line Terminal Shell Emulator
Ctrl+Alt+t on desktop
(Press “Enter” to Execute Commands)In case first see: Terminal QuickStart Guide.
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Installing Mate desktop for Ubuntu 15.04 Trusty.
You have Two Choices:
Mate Vanilla desktop (Classical Mate desktop)sudo apt-get install mate-desktop-environment-extras
Ubuntu Mate desktop (Mate Ubuntu Tweaked with Themes Integration)
sudo apt-add-repository ppa:ubuntu-mate-dev/ppa
sudo apt-get update
sudo apt-get install ubuntu-mate-core ubuntu-mate-desktop