SOLUTION: solve the system of equation using substitution to eliminate one variable. y=2x 3x+y=20 I don't know how to work this out.

Algebra ->  Quadratic Equations and Parabolas -> SOLUTION: solve the system of equation using substitution to eliminate one variable. y=2x 3x+y=20 I don't know how to work this out.       Log On


   

Question 499424: solve the system of equation using substitution to eliminate one variable.
y=2x
3x+y=20

I don't know how to work this out.
Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
y = 2x (given)
3x + y = 20 (given)
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substitute y=2x in the second equation
so, you simply replace the 'y' with '2x'
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3x + 2x = 20
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5x = 20
x = 4
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Now that you have x=4, you can find 'y'.
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y = 2x
y = 2*4
y = 8
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Now check your work using the other equation.
3x + y = 20
3x = 3*4 =12
y = 8
3x + y = 20
Correct.
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You also can use graphs to see where the two lines intersect (which is (4,8)).
graph%28500%2C500%2C-10%2C10%2C-10%2C10%2C2%2Ax%2C-3%2Ax%2B20%29
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Re-read the question to make sure you answer what was asked.
Answer:
x = 4
y = 8
.
Done.