I am assuming that you mistyped and meant to write 729^{1}/3. Written in radical notation it would be: 1√(729/3) = 1√243, (this is taking into account that a regular square root can be written as 2√X and a cube root would be 3√X). However, with roots, one can write the equation √4 as (4)^(1/2) which both would be equal to 2. So with the number you have written, it can be rewritten as (729/3)^1 which would be the same as 3/729.
If you just accidentally wrote the "" and the actual question is just (729^1)/3 then the answer would purely be 729/3 which is equal to 243.
12/1/2013

Calvin K.