FAQ: Variables - Arithmetic Operators

I am new to coding so I was doing the lesson Arithmetic Operators. I wanted to delete the written code at the beginning where we mostly have to change things and try from nothing. and I did it but when tried to compile it, it didn’t work why.
Here is a picture.

you forgot to include the iostream (io = InputOutput) library/header.

given cout is a output method in iostream library, not importing the library gives an error.

How do I add this iostream?

Its literally in the hint? I can see the hint with import/include in your screenshot

Thank you I did it.!