SOLUTION: how do you do substitution. like y=2x+7 and 3x-y=-9. if you could help plz

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Question 264187: how do you do substitution. like y=2x+7 and 3x-y=-9. if you could help plz
Answer by checkley77(12844) About Me  (Show Source):
You can put this solution on YOUR website!
y=2x+7 replace y with (2x+7) in the second equation & solve for x.
3x-y=-9
3x-(2x+7)=-9
3x-2x-7=-9
x=-9+7
x=-2 ans.
y=2*-2+7
y=-4+7
y=3 ans.
Proof:
3*-2-3=-9
-6-3=9
-9=-9