# How do you solve the system of equations x- 7y = 21 and 2x - 7y = 28?

Mar 26, 2018

$x = 7$ and $y = - 2$

#### Explanation:

$x - 7 y = 21$
$2 x - 7 y = 28$

Subtracting the second equation from the first equation:
$2 x - 7 y - \left(x - 7 y\right) = 28 - 21$
$2 x - 7 y - x + 7 y = 7$
$x = 7$

Plugging in $7$ for $x$ in the first equation:
$7 - 7 y = 21$
$7 = 21 + 7 y$
$7 y = 7 - 21$
$7 y = - 14$
$y = - \frac{14}{7}$
$y = - 2$