What is the value of 3/4 k to the 3rd power - 9 when K=3

So, I am assuming your problem looks like this: (3k/4) ^3

If that is true, then simply substitute 3 in for k so you get: [3 (3) / 4]^3

That is equal to (9/4) ^3 which is equal to (9/4) (9/4) (9/4) = (729/64)

So your answer is 729/64 or 11.390625