Answer
$\dfrac{3xy}{2ab}$
Work Step by Step
Cancelling the common factor between the numerator and the denominator, the given expression, $
\dfrac{-21xy}{-14ab}
,$ simplifies to
\begin{array}{l}\require{cancel}
\dfrac{\cancel{-7}\cdot3xy}{\cancel{-7}\cdot2ab}
\\\\=
\dfrac{3xy}{2ab}
\end{array}
