Thanks. But you guys are answering with more questions (and answers). What I really need is an explanation.
Well, what we are trying to do is making you think and understand why such and such things work... because we'll not always be here to answer you or to explain things to you. You'll have to be able to think on your own at some point and evaluate whether or not your thought is correct or not.
There is an assumption that you know something about index laws (otherwise why are you attempting this question). The point of being asked questions is to try and guide you to the answer yourself, based on what you already know. You were told everything you needed to know, the expectation was that you would attempt then to answer the question rather than maintaining a helpless attitude. Post #2 and then particularly post #7 tell you exactly what is required.
What I'd like to see is if you have actually learned anything from this thread. eg. What is 1/81 as a power of 3?