This is asking you to solve the equation ...
... 27 = 3^x
You can use logarithms to find
... log(27) = x·log(3)
... log(27)/log(3) = x = 1.43136376.../0.47712125...
... x = 3
Or, you can use your knowledge of small cubes and match exponents.
... 3^3 = 3^x
... 3 = x