## Elementary Algebra

$-\dfrac{3}{17}$
Cancelling the common factor between the numerator and the denominator, the given expression, $\dfrac{9}{-51} ,$ simplifies to \begin{array}{l}\require{cancel} \dfrac{\cancel{3}\cdot3}{\cancel{3}\cdot(-17)} \\\\= \dfrac{3}{-17} \\\\= -\dfrac{3}{17} \end{array}