SOLUTION: I have a test on this tomarrow. I am having a very hard time understanding the questions and how to do them. I have to solve the linear system by using elimination. The problem is

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Question 274441: I have a test on this tomarrow. I am having a very hard time understanding the questions and how to do them. I have to solve the linear system by using elimination. The problem is
3x=y-20
-7x-y=40
how do I do this kind of problem?
Found 2 solutions by stanbon, josmiceli:
Answer by stanbon(75887) (Show Source):
You can put this solution on YOUR website!
solve the linear system by using elimination. The problem is
3x=y-20
-7x-y=40
-------------------------
Rearrange the equations:
3x - y = -20
-7x -y = 40
------------------------
Subtract the 2nd equation from the 1st and solve for "x":
4x = -60
x = -15
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Substitute into 3x-y = -20 and solve for "y":
3(-15) - y = -20
-45 -y = -20
y = -45+20
y = -25
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Cheers,
Stan H.

Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website!
(1)
(2)
Whatever I do to one side of an equation, I must do to the other side
First, I want to subtract from both sides of (1)
(1)

(1)
Now multiply both sides of (1) by
(1)
Now add (1) and (2)
(2)
(1)

Now substitute this back into (1)
(1)
(1)

x = -6 and y = 2