What is the inverse of the function below? f(x) = x - 6

To compute the inverse function of F(x) you simply have to get how argument x depends of value F(x).
F(x)=x-6
Inverse function:
x = F(x)+6
To show that there are different mathematical objects just use e.g F(y)
F(y)=y+6 

What’s the equation you are trying to solve to get x?

The answer is: y would equal 3 because if you simplify the equation then it would be y= 3x+9 and if you divide 3x and 9 by 3 it would equal 3. y= 3