What is the inverse of the function f of x equals 1/9 x + 2

Converting an equation into inverse function, we need to interchange x with the y.
f(x) = 1/9x + 2
y = 1/9x + 2
Interchange x and y

x = 1/9y + 2
Get the y.

-1/9y = -x + 2
1/9y = x - 2
y = 1/9x - 2/9

So the final answer is
y = 1/9x - 2/9