# How do you solve x-y=9 and 2x+2y=2?

Nov 13, 2015
• Substitute one value by using the other
• Set equation 1 into equation 2
• Solve like a normal equation.

#### Explanation:

$1 : x - y = 9$
$2 : 2 x + 2 y = 2$

Rewrite equation 1:
$x = 9 + y$

Put $9 + y$ instead of $x$ in equation 2:
$2 \left(9 + y\right) + 2 y = 2$

Solve like normal:
$18 + 2 y + 2 y = 2$
#4y = -16

Divide both sides by 4:
$y = - 4$

Put this value into equation 1:
$x - \left(- 4\right) = 9$
$x + 4 = 9$
$x = 9 - 4$
$x = 5$

To sum it up; $x = 5$ and $y = \left(- 4\right)$