Chapter 1 - Introduction to Algebraic Expressions - 1.8 Exponential Notation and Order of Operations - 1.8 Exercise Set - Page 67: 85

$17x^2-17x$

Using $a(b+c)=ab+ac$ or the Distributive Property and then combining like terms, the given expression, $ 2x^2+5(3x^2-x)-12x $, simplifies to \begin{array}{l}\require{cancel} 2x^2+5(3x^2)+5(-x)-12x \\\\= 2x^2+15x^2-5x-12x \\\\= (2x^2+15x^2)+(-5x-12x) \\\\= 17x^2-17x .\end{array}