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

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Answer 1 · 2015-06-05T23:41:00

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

$d = 2 - e$

Then substitute this in the second equation to get:

$4 = d - e = (2 - e) - e = 2 - 2e$

Add $2e$ to both sides to get:

$2e+4 = 2$

Subtract $4$ from both sides to get:

$2e = -2$

Divide both sides by $2$ to get:

$e = -1$

Then

$d = 2 - e = 2 - (-1) = 2+1 = 3$

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