How do you solve for x: -3/4 x = 12?

Jul 21, 2016

$x = - 16$

Explanation:

There are a few ways of approaching the question, but they will all give the same answer.

Method 1. We can get rid of the denominator first, and then divide by -3 as a second step.

$\frac{\textcolor{b l u e}{\cancel{4} \times} - 3}{\cancel{4}} x = \textcolor{b l u e}{4 \times} 12$

(-3)/(color(red)(-3))x = 48/(color(red)(-3)

$x = - 16$

Method 2: multiply both sides by the reciprocal of $- \frac{3}{4}$

$- \frac{3}{4} x \times \textcolor{b l u e}{- \frac{4}{3}} = 12 \times \textcolor{b l u e}{- \frac{4}{3}}$

$x = 16$

Method 3. Because we have an equation with one fraction o each side, we can cross-multiply,

$- \frac{3}{4} x = \frac{12}{1}$

$- 3 x = 48$

$x = - 16$