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

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Answer 1 · 2018-03-26T04:46:57

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

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

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

Plugging in $7$ for $x$ in the first equation:
$7-7y = 21$
$7 = 21 + 7y$
$7y = 7-21$
$7y = -14$
$y = -14/7$
$y = -2$

How do you solve the system of equations x- 7y = 21x- 7y = 21 and 2x - 7y = 282x - 7y = 28?