What is the meaning of this question? Are you asking about the nature/significance of a number raised to a fractional power or are you actually looking for the numerical answer to 125^(2/3) ?!? If the former, the answer is solving for x in the equation [itex]125^{2/3}=x[/itex], which is equivalent to the equation [itex]125^2 = x^3[/itex], which means finding the number x such that raised to the power 3 equal 125 raised to the power 2. If the later, any calculator, even the cheapest, will tell you it's 25.
just to clarify 125^(2/3) the /3 means the third or cube root and the 2 can be taken to mean squared ince both are powers the Cube[(125^2)] will give you the answer. hope this makes it clear!