How do you solve x + y = 1 and 3x – y = 11?

Apr 11, 2018

$y = - 2$ and $x = 3$.

Explanation:

You need to use simultaneous equations. Make $x$ or $y$ the subject from one equation and substitute it into the other.

$x = 1 - y$

Then

$3 \left(1 - y\right) - y = 11$

$3 - 3 y - y = 11$

$3 - 4 y = 11$

$4 y = - 8$

$y = - 2$

If $y = - 2$, substitute back into either equation to find $x$.

$x - 2 = 1$

$x = 3$