When we talk about the distance between 2 numbers, we usually just
subtract those numbers to find the distance between them, so:

|x-9|<=8

In words, the absolute value of x minus 9 is less than or equal to 8 (it
can be 8, but it can't larger than 8, that is why we use less than or
equal to).

We don't know if x or 9 is the bigger number, and when talking about
distances, they can most often never be negative, that is where the
absolute value comes in to play.

I hope this helps! :)
Please best my answer and add me as your tutor for further help. Thanks :)