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Solve the following system of equations by linear combination: 3d – e = 7 d + e = 5

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3d - e = 7d + e = 5 ⇒ 3d - e = 5
7d + e = 5


3d - e = 5
7d + e = 5 +
-----------------------
10d / = 10
10d = 10
d = 10/10
d = 1

7d + e = 5
7×1 + e = 5
7 + e = 5
e = 5 - 7
e = -2

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