Answer
$\dfrac{a}{2b}$
Work Step by Step
The correct right side of the given incorrect equation, $
\dfrac{\left(\dfrac{a}{b}\right)}{2}=\dfrac{2a}{b}
,$ is
\begin{array}{l}\require{cancel}
\dfrac{a}{b}\div2
\\\\=
\dfrac{a}{b}\cdot\dfrac{1}{2}
\\\\=
\dfrac{a}{2b}
.\end{array}
