SOLUTION: I am working on solving the systems of equations by elimination method. {-x+18y=20 and x+18y=25}. Once these two equations are added together, I come up with 36y=45. The next st

Question 515614: I am working on solving the systems of equations by elimination method.
{-x+18y=20 and x+18y=25}. Once these two equations are added together, I come up with 36y=45. The next step is to solve for y by dividing 36y=45. My answer is y=5/4. So far, so good.
However, I am having trouble finding x. I rewrite the above equations and substitute 5/4 in the first equation, -x+18y=20. I substitute 5/4 for y and the answer is x-5/2. I need to know "how" that answer is worked out.
Thanks.
Answer by mananth(16946) (Show Source): You can put this solution on YOUR website!
I continue
x+18y= 25
x+18*5/4 = 25
LCD = 4
multiply by 4
4x+90=100
4x=10
x=10/4
x=5/2
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