A restaurant compiled the following information regarding 39 of its employees. Of these​ employees, 12 cooked​ food, 16 washed​ dishes, 25 operated the cash​ register, 6 cooked food and washed​ dishes, 6 cooked food and operated the cash​ register, 8 washed dishes and operated the cash​ register, and 2 did all three jobs. How many of the employees only cooked​ food?