Answer:
I think it is D. 9/15 * 14/20
It can be modeled by an exponential function, f(x) is divided by 3 each time x increases by 1.
This means that the base of the exponential function is 1/3, and since the value of f(x) when x=0 is 81, 
12% and 0.12 are the percentages and deciamls