SOLUTION: solve the system by elimination x+2y=9 3x-y=-15

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Question 785698: solve the system by elimination
x+2y=9
3x-y=-15
Answer by waynest(281) About Me  (Show Source):
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3(x + 2y) = 3(9)
3x + 6y = 27 subtract the other equation from this one.
-(3x - y = -15)
7y = 42
7y/7 = 42/7
y = 6
x + 2(6) = 9
x + 12 = 9
x = 9 -12
x = -3
check:
3(-3) - 6 = -15
-9 -6 = -15
-15 = -15
-3 + 2(6) = 9
-3 + 12 = 9
9 = 9