How do you solve the following system?: $3x -6y =21, -x -3y = -7$

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Answer 1 · 2017-10-08T10:15:59

$x= 7$ and $y = 0$

$3x -6y =21$ -----------Let this be equation(1), and
$-x -3y = -7$ ---------- Let this be equation(2)

From (2), by transposition method, we have :

$-x -3y = -7$

$-x = -7+3y$

$x = 7-3y$ ---------------let this be equation (3).

Substitute vale of $x$ from equation (3) in equation (1):

$3x -6y =21$

$3(7-3y) -6y =21$

$21 -9y -6y = 21$

$21 - 15y = 21$

$-15 y = 21-21$

$y = 0/-15$

$y =0$

From (3) , we can get value of $x$ :

$x = 7-3y$

$x = 7-3(0)$

$x = 7-0$

$x = 7$

therefore we have:

$x= 7$ and $y = 0$

Cross check by substituting values of $x$ and $y$ in equation (2):
$-x -3y = -7$
$-7 -3(0) = -7$
$-7 -0 = -7$
$-7 = -7$

How do you solve the following system?: 3x -6y =21, -x -3y = -73x -6y =21, -x -3y = -7