Answer
(a) $f(6)=1$
(b) $f(-6)=-1$
Work Step by Step
RECALL:
$f(a)$ represents the value of the function $f$ when $x=a$.
Replace $x$ with the given value to obtain:
(a)
$f(6) = \dfrac{6}{|6|}
\\f(6)= \dfrac{6}{6}
\\f(6)=1$
(b)
$f(-6) = \dfrac{-6}{|-6|}
\\f(-6)= \dfrac{-6}{6}
\\f(-6)=-1$