To find the inverse of the the function, it must be arranged in such a way that the independent variable be on the left side and the dependent variable on the right. So,
f(x) = y = 3x/ (8 + x)
y (8 + x) = 3x
8y + xy = 3x
8y = 3x - xy
8y = x (3 - y)
8y / (3-y) = x
x = 8y / (3 -y)
Therefore,
f-(x) = f(y) = x = 8y/ (3 - y)
