Error unexplainable

I can’t see what I do wrong
see link

Hi there. We can’t see your code, so we will need you to copy-paste your code into a forum post so that we can help.

When you enter a code block into a forum post, please precede it with a separate line of three backticks and follow it with a separate line of three backticks to make it easier to read.

You can also use the “preformatted text” tool in the editor (</>) to add backticks around text.

See this post to find the backtick on your keyboard.
Note: Backticks (`) are not single quotes (’).