## Elementary Algebra

$\dfrac{3xy}{2ab}$
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}