When a number is raised to a fraction you basically look at it in two ways.
The denominator tells you what # root you have to take so in this case it is 3 so that means that first you take the cubed root of the number 64 which is four. The numerator then tells you how many times to multiply that number by its self. So in this case you take 4 and you mulitply by itself 2 times so 4*4 is equal to 16
