You have to specify what you mean here... this could be
(3√27) * 6
or
3√27*6
Depending on which problem you're trying to solve, your answer would be
(3√27) * 6 = 3*6 = 18
or
3√27*6 = 3√162 = 5.451361778496419
I'm thinking your probably looking for the first answer.