Chapter 1 - Introduction to Algebraic Expressions - 1.7 Multiplication and Division of Real Numbers - 1.7 Exercise Set - Page 58: 113

$-3$

The given expression, $ \left( -\dfrac{18}{7} \right) + \left( \dfrac{3}{-7} \right) $, simplifies to \begin{array}{l}\require{cancel} -\dfrac{18}{7}-\dfrac{3}{7} \\\\= \dfrac{-18-3}{7} \\\\= \dfrac{-21}{7} \\\\= -3 .\end{array}