you need to take the average of the column that is created here with this line: Count (Priem. [ID_klienta]) as kol

This is my query:

Select Seller.FIO as 'ФИО продавца' Count(Priem.[ID_klienta]) as kol From (Priem left join Saller on Priem.[ID_klienta]= Saller.ID_saller) Group by Seller.FIO; 

and I need to take the average of the column that is created here with this line:

 Count(Priem.[ID_klienta]) as kol