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.