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New to linux... I have no idea how to fix this error...
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Since OP is new to linux I'll just add this in case it's helpful.
To edit a file owned by root (super account) you can use sudoedit /etc/apt/sources.list or alternatively sudo nano /etc/apt/sources.list in a terminal.
In the editor save by using the key combo Ctrl+S and exit with Ctrl+X.
Commenting is adding a # in front of the line.
so the file should look like something like this
# deb cdrom:[Debian GNU/Linux 11.5.0 _Bullseye_ - Official amd64 NETINST 20220910-10:38]/ bullseye main