Unknown error in using "let" feature

When I was attempting to follow along with the " Updating Documents: replaceOne()" exercise, it let me set filter = title … but when I tried to set let = doc I encountered repeated issues. when I try and bring up by typing “doc” after entering the data it comes up as null. Is this normal?

Hi @Allison_Keats_70328,

I might be able to help you better if I can get this some extra information about your issue.

Please share the screenshot of the command that you typed in terminal along with the error message.

Thanks,
Sonali