Question

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

Answer 1

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


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

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