An irrational number between 5/7 and 7/9 is?
There are infinitely many irrational numbers between 5/7 and 7/9.
(0.7507500075000.... is also an irrational number between 5/7 and 7/9;but it is not the only one;there are many others)
Here are some:
4/17π,5/21π,6/25π,7/29π,7/30π,8/33π,8/35π,....