Answer
$\frac{1}{x}$
Work Step by Step
Let $y= \ln(35 x)$ and substitute $t=35x$.
Then, $y=\ln t$.
According to the chain rule, we have
$\frac{dy}{dx}=\frac{dy}{dt}\cdot\frac{dt}{dx}=\frac{1}{t}\cdot35= \frac{1}{35x}\cdot35$
$=\frac{1}{x}$