Track / Stage 1 / 176 of 240 #176 of 2444

Problem 176

Algebra Difficulty 1.6 Find the answer CEMC Pascal · Canada · 2020

Which of the following expressions is not equivalent to $3x+6$ ?

$3(x+2)$
$\dfrac{-9x-18}{-3}$
$\dfrac{1}{3}(3x)+\dfrac{2}{3}(9)$
$\dfrac{1}{3}(9x+18)$
$3x-2(-3)$

Your answer

A number or a short expression. Fractions can be typed as 3/2, and spacing doesn't matter.

Official solution

We look at each of the five choices:

$3(x+2) = 3x + 6$
$\dfrac{-9x-18}{-3} = \dfrac{-9x}{-3} + \dfrac{-18}{-3} = 3x + 6$
$\dfrac{1}{3}(3x) + \dfrac{2}{3}(9) = x + 6$
$\dfrac{1}{3}(9x+18) = 3x + 6$
$3x - 2(-3) = 3x + (-2)(-3) = 3x + 6$

The expression that is not equivalent to $3x+6$ is the expression from (C).

Source: CEMC, University of Waterloo, licensed CC-BY-NC-4.0. Statement reproduced verbatim; metadata (topic, difficulty, ordering) added by this project.