# How do you solve y=2x and y=12-x?

May 12, 2016

$\left(x , y\right) = \left(\textcolor{b l u e}{4 , 8}\right)$

#### Explanation:

If
$\textcolor{w h i t e}{\text{XXX}} y = 2 x$
and
$\textcolor{w h i t e}{\text{XXX}} y = 12 - x$

then
$\textcolor{w h i t e}{\text{XXX}} 2 x = 12 - x$

Adding $x$ to both sides
$\textcolor{w h i t e}{\text{XXX}} 3 x = 12$

Dividing both sides by $3$
$\textcolor{w h i t e}{\text{XXX}} x = 4$

Substituting $4$ for $x$ back in $y = 2 x$ gives
$\textcolor{w h i t e}{\text{XXX}} y = 8$