Instead of doing your problem, I will do one EXACTLY in every detail like
your problem.  Then you can use it as a model to do yours by:

I will do this one:

I start by assuming the general power formula for g(x)



I substitute x=3 and set that equal to 4/3:



Then I substitute x=4 and set that equal to 4/9:



Then I divide equals by equals dividing g(4) by g(3)



        

        

I substitute that in 

              

              

I multiply both sides by 27 to clear of fractions:

              

              

Therefore my power function  becomes
              
Answer:       

Now do your problem exactly the same way I did mine.

Edwin