SOLUTION: SOLVE SYSTEM EQUATION BY SUBSTITUTION. 4X+Y=18 y=2x

Question 314621: SOLVE SYSTEM EQUATION BY SUBSTITUTION.
4X+Y=18
y=2x
Found 2 solutions by Fombitz, rapaljer:
Answer by Fombitz(32388) (Show Source): You can put this solution on YOUR website!
1.
2.
Substitute eq. 2 directly into eq. 1,

Now use eq. 2 for y,

.
.
.

Answer by rapaljer(4671) (Show Source): You can put this solution on YOUR website!
Substitute the y=2x back into the first equation:
4x+y=18
4x+( )=18
4x+(2x)=18
6x=18
x=3

Now find y using the y=2x equation:
y=2x
y=2(3)
y=6

Check in the other equation:
4x+y=18
4*3+6=18
It checks.

For additional explanation on this topic, please see my own website. Click on my tutor name "rapaljer" and then click on the link that is given there. From my Homepage, look for the link "Basic, Intermediate, and College Algebra: One Step at a Time." Select "Basic Algebra," and look for "Chapter 4", Section 4.07 Systems of Equations." These sections include my own explanation written especially for students who may have trouble understanding these skills, examples, exercises, and ALL the answers. Many of the exercises are solved in detail on the "Math in Living Color" pages that go with these pages.

Dr. Robert J. Rapalje, Retired
Seminole State College of Florida
Altamonte Springs Campus
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