It is not as tough a problem as it seems to you. You can easily grasp the problem, once it is done,
9 5/9 - 6 5/6 = 86/9 - 41/6
= (172 - 123)/18
= 49/18
= 2 13/18
I hope that the simplification process is simple enough for you to understand. I also hope that this is the answer that you were looking for and the answer has actually come to your desired help.