20/9 in simplest form would be 2 2/9
What you would do is see how many times your denominator can go into your numerator. 9 goes into 20 two times. So you would take your two and put it on the outside as a whole number. Then you would take your left over two and make it you numerator. Therefore you will get 2 2/9 as your answer.
HOPE THIS HELPS! ^_^