[jaspreet2142]

I tried to run because command in ubuntu 7.10 but it show me message that
Because command is not installed try installing it by entering ubuntu disk in your
Drive and type sudo apt-install because
When I tried it it shows that enter ubuntu 7.10 gusty gibbon cd

[AskGary]

Try the command 'sudo apt-get install bc'

If this does not work, use the Package Manager to search and re-install.

[bendingoutward]

Here's the thing... even using apt-get directly, you'll still be prompted for the CD. You'll need to edit your repo file ( /etc/apt/something I believe ) to remove the cdrom device as one of the viable repositories. After that, either of AskGary's suggestions should work smashingly.