We have a fraction of two integers, so 25/9 is rational. A rational number is any fraction of two integers (as long as the denominator is not zero).
Something that is irrational would be pi = 3.14159... where we cannot write it as a fraction of two integers. We can get approximations such as 22/7, but we cannot land exactly on pi with a fraction like this. Another irrational value is sqrt(2).
Something like sqrt(25) is rational though because sqrt(25) = 5 = 5/1.
