# How do you solve by substitution d + e = 2 and d - e = 4?

Jun 5, 2015

Subtract $e$ from both sides of the first equation to get:

$d = 2 - e$

Then substitute this in the second equation to get:

$4 = d - e = \left(2 - e\right) - e = 2 - 2 e$

Add $2 e$ to both sides to get:

$2e+4 = 2$

Subtract $4$ from both sides to get:

$2 e = - 2$

Divide both sides by $2$ to get:

$e = - 1$

Then

$d = 2 - e = 2 - \left(- 1\right) = 2 + 1 = 3$