SOLUTION: How do I solve the system by substitution? 3x – y = –7 x + y = –9

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Question 81689: How do I solve the system by substitution?
3x – y = –7
x + y = –9
Answer by checkley75(3666) About Me  (Show Source):
You can put this solution on YOUR website!
3X-Y=7
X+Y=-9
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4X=-2
X=2/-4
X=-1/2 ANSWER.
-1/2+Y=-9
Y=-9+1/2
Y=-17/2 ANSWER.
PROOF
-1/2-17/2=-9
-18/2=-9
-9=-9