Update Manager, Live USB 12.04 LTS (with persistence), Firefox

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http://askubuntu.com – I am new to Ubuntu. I have a Live USB running 12.04 LTS. I also still have Firefox version 12.0+build1-0ubuntu0.12.04.1 installed and want to upgrade to version 19. I have searched a bit and my understanding is that Firefox updates are now part of the main system updates. When I run Update Manager I am told that everything is up to date. I tried running Synaptic to see if is would see a newer version of Firefox and it does not provide an update option for Firefox. I am thinking that I might be able to uninstall and reinstall Firefox but much rather get the update working. (HowTos)