Question

There are 26 non square number between 6 and 8 is it true?

Answer 1

between 6 and 8  we are looking for 26 non-square numbers ie., numbers which are not perfect squares.

There are infinite real numbers with decimals between 6 and 8. So there are infinite number of square numbers and infinite number of non-square numbers too. 

     6.1, 6.11, 6.2, 6.3, 6.4 , 6.5, 6.55, 6.6, 6.66, 6.76, ... 7, 7,1, 7,2 , ..7.99,

You can find many like this.

If you are looking for integer numbers, obviously the answer is false.