SOLUTION: Solve the system by substitution. 3x - y = -7 x + y = -9

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Question 72936: Solve the system by substitution.
3x - y = -7
x + y = -9
Answer by funmath(2933) About Me  (Show Source):
You can put this solution on YOUR website!
Solve the system by substitution.
3x - y = -7
x + y = -9
Solve the second equation for x or y, whichever you prefer, there's a few choices. I'm going with x
x+y-y=-9-y
x=-9-y Now substitute this in for x in the first equation and solve for y.
:
3%2Ahighlight%28-9-y%29-y=-7
3%28-9-y%29-y=-7
-27-3y-y=-7
-27-4y=-7
-27%2B27-4y=-7%2B27
-4y=20
-4y%2F-4=20%2F-4
y=-5
Now substitute this into the second equation for y and solve for x.
x%2Bhighlight%28-5%29=-9
x-5=-9
x-5%2B5=-9%2B5
x=-4
The solution to the system is: (x,y)=(-4,-5)
Happy Calculating!!!!