# How do you solve x+y=1 and x-y=2  using substitution?

Apr 11, 2016

(1.5, -0.5)

#### Explanation:

$x + y = 1$
$x + y - y = 1 - y$
So $x = 1 - y$
Substitute this x-value into the second equation.

$\left(1 - y\right) - y = 2$

$1 - 2 y = 2$

$1 - 2 y - 1 = 2 - 1$

$- 2 y = 1$

$\frac{- 2 y}{-} 2 = \frac{1}{-} 2$

$y = - 0.5$

Substitute this answer into the original formula

$x + \left(- 0.5\right) = 1$

$x + \left(- 0.5\right) + \left(0.5\right) = 1 + \left(0.5\right)$

$x = 1.5$

Check by substituting into the second formula.

$1.5 - \left(- 0.5\right) = 2$

$2 = 2$