Answer
$y'=-\dfrac{1}{(x-2)^2}.$
Work Step by Step
$y=\dfrac{1}{(x-2)}=(x-2)^{-1}.$
Using the Chain Rule:
$u=(x-2)$; $\dfrac{du}{dx}=1$
$\dfrac{dy}{du}=-\dfrac{1}{u^2}$
$\dfrac{dy}{dx}=\dfrac{dy}{du}\times\dfrac{du}{dx}=-\dfrac{1}{(x-2)^2}.$