The post that was sited as the reason for closing my question, does nothing to help me if I can't comment on it to ask how to fix my problem!
Firstly your question was off-topic.
Secondly your question was a duplicate.
/etc/apt/sources.list.d/ is empty on a new install (of on-topic Ubuntu systems), so anything in that file was added by a user with
Your error told you line 1 of the file mentioned in the error message contained error(s), ie.
echo is not a valid keyword used in sources files. That file needed to be edited & corrected to match your system.
Linux Mint provides system(s) based on Ubuntu, and system(s) based on Debian, your picture of a file contained a mixture of both Debian & Ubuntu - thus was invalid even if the echo was ignored. Your question however was off-topic on this site, which deals only with Ubuntu (Debian isn't on-topic, unless the question is specific to how Ubuntu & Debian interact, as both teams often do).
Don't forget this site is an official Ubuntu support site; I can access it using only my Ubuntu SSO/signon, though I can't access CHAT services as they require a Stack Exchange signon. You're likely accessing it via Stack Exchange, where 'SE Unix & Linux' covers your Operating System, not this Ubuntu only site.
It's common for folks who do not understand an answer to understandably complain that an answer is not helpful...or to mistakenly claim that an answer is not applicable or not duplicate.
Keep in mind that we are a community of volunteers. Few here are professional documentation writers or professional support engineers, and there is no training for these volunteers. We rely on YOU to help improve answers for future readers.
Please help improve answers by using the editing tools.
Or offer your own clearer, more accurate, better-written answer after you solve the problem.