7/8 (< > =)5/9 13/21(< > =)10/13 9/10(< > =)8/15 16/20( < > =)10/25

7/8 > 5/9 is true so there are infinitely many solutions

13/21 < 10/13 is true so there are infinitely many solutions

9/10 > 8/15 is true so there are infinitely many solutions

For the last one I'm a explain:

1. simplify 16/20 to 4/5

2. simplify 10/25 to 2/5

Since 4/5 > 2/5 is true, there are infinitely many solutions so basically in terms: 16/20 > 10/25 is true so infinitely many solutions.