Question 286132: I do not know how to solve system equations using substitions with fractions. Do i multiply by a common denominator?
here is an example if you could solve it step by step for me:
7x-y=10
x=1/3y-2
i know the answer (4,18) but not how to get there. if you can help it would be greatly appreciated thank you.
Answer by ptaylor(2198)   (Show Source):
You can put this solution on YOUR website! I'm confused. In the second equation is it 1/(3y) or (1/3)y. I will assume that it's the latter, so:
7x-y=10-------------------------eq1
x=(1/3)y-2---------------------eq2
If we get rid of the fraction in eq2, then you may not have to worry about it, so:
Multiply each term in eq2 by 3 and we get
3x=y-6 add 6 to each side
3x+6=y----eq2a
now substitute 3x+6 for y in eq 1
7x-(3x+6)=10
7x-3x-6=10 add 6 to each side
7x-3x-6+6=10+6 collect like terms
4x=16
x=4
substitute x=4 into eq2a and we get:
3*4+6=y
y=18
Hope this helps---ptaylor
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