Chapter 1 - Some Basic Concepts of Arithmetic and Algebra - 1.5 - Use of Properties - Problem Set 1.5 - Page 34: 80

$150$

The given expression, $ 5x-6x+x-7x-x-2x ,$ simplifies to \begin{array}{l}\require{cancel} -x+x-7x-x-2x \\\\= 0-7x-x-2x \\\\= -8x-2x \\\\= -10x .\end{array} Substituting $ x=-15 ,$ the resulting expression above evaluates to \begin{array}{l}\require{cancel} -10(-15) \\\\= 150 .\end{array}