# Math Help - simultaneous equation

1. ## simultaneous equation

$-3x+y=15
x=2-2y$

2. Originally Posted by johnsy123

$-3x+y=15
x=2-2y$

Just FYI Tex editor's don't recognize white space inside math tags so that is really hard to understand.

$-3x+y=15$
$x=2-2y$

subbing the 2nd equation into the first gives

$-3(2-2y)+y=15 \iff -6+6y+y=15 \iff 7y=21 \iff y =3$

Now sub in to find x $x=2-2(3)=-4$ so the solution is

$(-4,3)$