# How do you solve the system 2x + y = 0 and 3x - y = - 10?

May 16, 2015

One easy way to think this problem is by isolating one variable in one equation and substitute the value you find in the second equation, as follows:

For example, let's isolate $y$ in the first equation:

$y = - 2 x$

Now, let's just substitute this value we found in the second equation:

$3 x - \left(- 2 x\right) = - 10$
$5 x = - 10$
$x = \left(- \frac{10}{5}\right) = - 2$

Now, we know $x = - 2$ and we can complete the value of $y$, because we already know that $y = - 2 x$

Then, $y = - 2 \left(- 2\right)$.
$y = 4$.