Question

how are you see if the barber in a saloon has cut the hair on your neck properly or not​

Answer 1

How you are able to see the hair is cut properly  or not on your neck.

Explanation:

If you are going to a barber in a saloon and after hair cutting. You want to know that the hair on your neck is cut properly or not. So, you can ask the barber to stand behind you and show the small mirror at a certain angle so that you can see your hair in the mirror which was in front of you. So that you can check the barber has cut the hair on your neck properly or not.