Why is 6/8 greater than 5/8 but less than 7/8

Simple!

Since we can observe that they all have the same denominators (bottom part) we can just observe the numerator (top part)

6 is indeed greater than 5, yes? So we can safely say that

6/8 > 5/8

Now the for the second part. 

6 is smaller than 7, yes? So we can make the observation that

6/8 < 7/8

Hope that makes sense! (Be sure to thank me, plz)

P.S. If you want an example of unlike denominators, let me know.