Q: i need helpe my 4 old coputer is damge and i have only 2 new how can i cancel other 4 computer from athurty??

You will need to deauthorize all computers and then reauthorize the ones that are still working: See the instructions below from Deauthorize your computer using iTunes - Apple Support

Deauthorize all computers

Open iTunes on one of your authorized computers.

 

1. Click Store > Sign In.
2. Enter your Apple ID and password.
3. Click Deauthorize All.
   
   The Deauthorize All button appears only if you have more than 2 authorized computers. If you don't see the Deauthorize All button, that means you only have one authorized computer.

 

I deauthorized all of my computers. What should I do now?

Reauthorize each computer that you want to use with iTunes. To reauthorize:

• Go to Store > Authorize this computer.
• Enter your Apple ID and password.
• Click Authorize.