x^3 = 27/64
x = cube root(27/64)
x = cube root(27) / cube root(64)
x = 3/4
.
Note: When you do something like x^2 = 25 and you get x = 5, you actually get x = 5 or -5 because 5^2 = 25 and (-5)^2 = 25. This only happens with even numbered exponents like x^2, x^4, x^6 and so on. If x^4 = 81, then x = 3 or -3, but if x = 27, then x = 3 (because 3^3 = 27, whereas (-3)^3 = -27 ).