I am trying to take a derivative of the function below with respect to X. The problem is X is both in the numerator and in the exponential function in the denominator. I don't know how to get the .4X-7.8 out of the exponential function and then combine with the 16X to simplify and take a derivative? I was trying to use ln() somehow but can't seem to figure it out. Thanks!

$\displaystyle f(x)=(X-5)(15)\frac{1}{1+e^{0.4X-7.8}} $