Hello!
First of all, we know the 6/11 is greater than 6/13. If we find a common denominator with 5/10 and 6/11, we get 55/110 and 60/110. So now it's between 6/11 and 4/9.
The common denominator there is 99. This would give us 54/99 and 44/99.
Therefore, 6/11 is the greatest number.
I hope this helps!