# What are x and y if x+y=4 and y=-7x+4?

Apr 11, 2018

#### Explanation:

$x + y = 4$ ---(1)

$y = - 7 x + 4$ ---(2)

The $x$ s and $y$ s in the question are of the same value. This means that you can substitute the value of $y$ in the second equation into the first equation:

$x + \left(- 7 x + 4\right) = 4$

This allows you to find $x$:

$x - 7 x + 4 = 4$

$- 6 x = 0$

$x = 0$

Then this value can be substituted into either of the given equations:

$0 + y = 4$

$y = 4$

So $x = 0$ and $y = 4$.