Chapter 1 - Introduction to Algebraic Expressions - 1.7 Multiplication and Division of Real Numbers - 1.7 Exercise Set - Page 59: 120

$-\dfrac{3}{2}$

The given expression, $ \left( \dfrac{-3}{5} \right)\div\dfrac{6}{15} $, simplifies to \begin{array}{l}\require{cancel} \left( \dfrac{-3}{5} \right)\cdot\dfrac{15}{6} \\\\= \dfrac{-3(15)}{5(6)} \\\\= \dfrac{-\cancel{3}(\cancel{5}\cdot3)}{\cancel{5}(\cancel{3}\cdot2)} \\\\= \dfrac{-3}{2} \\\\= -\dfrac{3}{2} .\end{array}