Solving a proportion with a variable

J

jjhai

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Aug 9, 2013
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3
Hello,

I'm trying to solve this problem:

x - 9 = _ 11
x . . . . . . 8

I think it should be put into these equations:

8 (x - 9) = x * 11

Whats throwing me off is the negative fraction. Does that make both the 11 and 8 negative?
 
Last edited:
You can choose one or the other to be negative, but not both.
 
Thank you both.

So then if I make the 11x negative, I end up with -72/-19 = x and therefore my answer should be positive 72/19 = x?
 
You could also multiply both sides by -1 to obtain:

\(\displaystyle \displaystyle \frac{9-x}{x}=\frac{11}{8}\)

Cross-multiply:

\(\displaystyle 8(9-x)=11x\)

\(\displaystyle 72-8x=11x\)

\(\displaystyle 72=19x\)

\(\displaystyle x=\dfrac{72}{19}\)
 
jjhai said:
Thank you both.

So then if I make the 11x negative, I end up with -72/-19 = x and therefore my answer should be positive 72/19 = x?
Click to expand...
Yes, and if you make the "8" negative you get -8x + 72 = 11x, as Denis said, and so 72= 19x which again gives x= 72/19.
 
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