If you cross multiply you will see that 1/3 is least 1/2 or 15/30 is in the middle and 2/3 it greatest. Or put it on a numberline
Explain how you know that 15/30 is greater that 1/3 but less than 2/3?
15/30 is equal to 1/2, because as you should know, 15 is half of 30. A simple way to do this in your head, is that 1/2 equals 1.5/3 (since 1.5 is half of 3). 1.5/3 is bigger than 1/3 simply because 1.5 is bigger than 1, and 1.5/3 is smaller than 2/3 simply because 1.5 is smaller then 2. Hope this helps!