Answer
$\dfrac{x+4}{x-4}$
Work Step by Step
Adding the numerators and copying the common denominator, the given expression, $
\dfrac{4}{x-4}+\dfrac{x}{x-4}
,$ simplifies to
\begin{array}{l}\require{cancel}
\dfrac{4+x}{x-4}
\\\\=
\dfrac{x+4}{x-4}
.\end{array}
