# What is the derivative of f(x)=ln(ln(7x))+ln(ln(6))?

You can use the Chain Rule where: given a function $y = f \left[g \left(h \left(x\right)\right)\right]$ you get:
$y ' = f ' \left[g \left(h \left(x\right)\right)\right] \cdot g ' \left(h \left(x\right)\right) \cdot h ' \left(x\right)$
In your case both $f \mathmr{and} g$ are log functions anf $h$ is $7 x$. So you get:
$f ' \left(x\right) = \frac{1}{\ln} \left(7 x\right) \cdot \frac{1}{7 x} \cdot 7 = \frac{1}{x \ln \left(7 x\right)}$
The last log, $\ln \left(\ln \left(6\right)\right)$, is a constant so its derivative is zero.