Question 638335: I need help with solving this system of equation by substitution.
2x-4y=40
8x-3y=82
Thanks!
Answer by josh_jordan(263)   (Show Source):
You can put this solution on YOUR website! To solve this system of equations by substitution, you will need to need to isolate one of your letters from one of your equations. With this problem, the easiest variable to isolate is x, since we can divide our entire first equation by 2 and not wind up with any fractions. So, when we divide our first equation by 2, we end up with:
Now, to isolate x, add 2y to both sides of the equation:
 , which equals:
From here, just subtitute 20+2y for x in your second equation:
Multiply 8 by everything in the parenthesis and add that result to -3y:
 , which equals:
Subtract 160 from both sides:
 =
Divide both sides by 13 to get y by itself:
 =-6
So, y=-6
Now, just substitute -6 for y in either equation. We will use the first equation:
 =
 =
 =
x=8
Our final answer is: x=8, y=-6
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