# How do you solve for a in 7a - b = 15a?

Feb 15, 2016

$a = - \frac{b}{8}$

#### Explanation:

Given
$\textcolor{w h i t e}{\text{XXX}} 7 a - b = 15 a$

Add $b$ to both sides
$\textcolor{w h i t e}{\text{XXX}} 7 a = 15 a + b$

Subtract $15 a$ from both sides
$\textcolor{w h i t e}{\text{XXX}} - 8 a = b$

Divide both sides by $\left(- 8\right)$
$\textcolor{w h i t e}{\text{XXX}} a = - \frac{b}{8}$