I WANT to install Adobe Flash, but it said you can not install because your computer is (amd64). What can I do to install Flash?

sudo apt-key adv --recv-key --keyserver keyserver.ubuntu.com 40976EAF437D05B5

Will add the key for the PPA you added but failed to add the key.

You cannot install "Adobe", it's a company, just like you can't install "microsoft" but you can install "Microsoft Word". "Adobe" is not a software

You can run:

sudo add-apt-repository ppa:sevenmachines/flash; sudo apt-get update && sudo apt-get install flashplugin64-installer

And it will install 64bit flash

Follow the next steps:

1) Save this to a text fle since you need to close your web browser (Firefox, etc)

2) Close Firefox or other Web browser

3) Open the Terminal from menu Applications------->Accesories------>Terminal

4) Copy and paste the following (It uninstall the previous installed Flash):

sudo apt-get remove -y --purge flashplugin-nonfree gnash gnash-common mozilla-plugin-gnash swfdec-mozilla libflashsupport nspluginwrapper

5) Copy and paste the following (one by one and then enter, then copy the next):

sudo rm -f /usr/lib/mozilla/plugins/*flash*
sudo rm -f ~/.mozilla/plugins/*flash*
sudo rm -f /usr/lib/firefox/plugins/*flash*
sudo rm -f /usr/lib/firefox-addons/plugins/*flash*
sudo rm -rfd /usr/lib/nspluginwrapper

6) wget http://download.macromedia.com/pub/labs/flashplayer10/flashplayer_square_p2_64bit_linux_092710.tar.gz

7) tar zxvf flashplayer_square_p2_64bit_linux_092710.tar.gz

8) sudo cp libflashplayer.so /usr/lib/mozilla/plugins/

9) sudo ln -sf /usr/lib/mozilla/plugins/libflashplayer.so /usr/lib/firefox-addons/plugins/

10) sudo ln -sf /usr/lib/mozilla/plugins/libflashplayer.so /usr/lib/xulrunner-addons/plugins/

11) sudo rm -rf libflashplayer.so

12) sudo rm -rf libflashplayer-10.0.45.2.linux-x86_64.so.tar.gz

13) Log out and Lob back in (not necesary, but just in case)

14) Enjoy! (You can use Flash now)