Question

input =9 output = 2 what is the function.

input = 27 output = 8 what is the function.

input = 42 output = 13 what is the function
input = 3 output = 0 what is the function.

Answer 1

f(x) = 28 x /126 or f(x) = x-7 or a zillion others will yield 2 if you put in 9 for x

What is the rest of the problem or are these all supposed to be one problem or what?

Answer 2

There's not enough information here to answer those. There are infinitely many functions that sent 9 to 2. For example, it could be f(x)=(x/3) - 1, f(x) = (x-1)/4, f(x) = x-7, f(x) = x^2 - 79, f^x = x^(1/2) - 1, f(x) = 2x-16, or any of infinitely many others. We need more than one input/output pair per function. The more, the better.