when you put 31/6 to 5 1/6 and 8 2/9 to 8 2/9 and 11/2 to 5 1/2. Then you change the denominators to 18, so you get 5 3/18 + 8 4/18 - 5 9/18. So you add the 5 3/18 and 8 4/18 to get 13 7/18. Then you subtract 13 7/18 by 5 9/18 to get 7 8/18. simplest form you will get 7 4/9. Your welcome.