# How do you solve the system x + 4y = 28 and - x + 4y = 20?

Jun 14, 2015

$\left(x , y\right) = \left(4 , 6\right)$

#### Explanation:

[1]$\textcolor{w h i t e}{\text{XXXX}}$$x + 4 y = 28$
[2]$\textcolor{w h i t e}{\text{XXXX}}$$- x + 4 y = 20$

[3]$\textcolor{w h i t e}{\text{XXXX}}$$8 y = 48$
dividing by 8
[4]$\textcolor{w h i t e}{\text{XXXX}}$$y = 6$

substituting $6$ for $y$ (from [4]) in [1]
[5]$\textcolor{w h i t e}{\text{XXXX}}$$x + 4 \left(6\right) = 28$
simplifying
[6]$\textcolor{w h i t e}{\text{XXXX}}$$x = 4$