What number is greater than 5 but less than 5.75?

Answer 1

There are infinitely many such numbers. For example:

5.00001

5.000011

5.0000111

5.00001111

5.00001112

5.00001234

and so on.

And, between any two of these, there are infinitely many numbers. And between any two of them ...

Answer 2

There are infinitely many numbers between any two different numbers. If you want the number that's exactly in the middle, take the average.