In a rational exponent the numerator represents the integer exponent, and the denominator represents the root. For 3/3:
Following the rules of exponents, you can easily simplify this expression to equal x because (3)(1/3)=1.
This is how you end up with rational exponents in the first place. The exponent of the root of a function is 1/root. Therefore, when you multiply an integer exponent to a root exponent you end up with (integer)(1/root)=(integer/root).
To illustrate with another example:
Following the rules of exponents that state that a variable to the exponent m raised to the exponent n equals the variable to the power of m times n