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.

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) (Show Source): You can put this solution on YOUR website!
y = 2x (given)
3x + y = 20 (given)
.
substitute y=2x in the second equation
so, you simply replace the 'y' with '2x'
.
3x + 2x = 20
.
5x = 20
x = 4
.
Now that you have x=4, you can find 'y'.
.
y = 2x
y = 2*4
y = 8
.
Now check your work using the other equation.
3x + y = 20
3x = 3*4 =12
y = 8
3x + y = 20
Correct.
.
You also can use graphs to see where the two lines intersect (which is (4,8)).

.
Re-read the question to make sure you answer what was asked.
Answer:
x = 4
y = 8
.
Done.

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