Answer
$\dfrac{3}{4}$
Work Step by Step
Factor 21 and 24 to obtain:
$=\left(-\dfrac{6}{7}\right)\left(-\dfrac{7(3)}{6(4)}\right)$
Cancel the common factors to obtain:
$\require{cancel}
=\left(-\dfrac{\cancel{6}}{\cancel{7}}\right)\left(-\dfrac{\cancel{7}(3)}{\cancel{6}(4)}\right)
\\=(-1) \cdot \left(-\dfrac{3}{4}\right)
\\=\dfrac{3}{4}$
