Chapter 1 - Some Basic Concepts of Arithmetic and Algebra - Chapter 1 Review Problem Set - Page 38: 67

$9$

Substituting $a= -1 $ and $b= -3 ,$ the given expression, $ (a-b)-(a+b)-b ,$ evaluates to \begin{array}{l}\require{cancel} (-1-(-3))-(-1+(-3))-(-3) \\\\= (-1+3)-(-1-3)+3 \\\\= 2-(-4)+3 \\\\= 2+4+3 \\\\= 6+3 \\\\= 9 .\end{array}