# I saw your PS late....

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Posted by Subhotosh Khan on October 11, 2002 at 16:06:27:

: OK, here's the problem. I got one answer, my book got a different answer, and my calculator says both are wrong. Here's the equation:

: 1/8x-1/7x=2, solve for x

: I got:
: 7/56x-8/56x=2
: -1/56x=2
: -56x^-1=2
: -28x^-1=1
: x=28

: The book got:
: 1/7x-1/8x=2 ....This is not the same problem you wrote on top
: 7-8=112x
: -1=112x
: x=-1/112

: My calculator got:
: 1/8x-1/7x=2, x=-112 (using q solver), when I substituted -112 for x, it came out equaling 2
: (1/{8[-112]}-1/{7[-112]}=2).

: I know the calculator is right, and I did find a way to get that answer, and I also see how I got my answer and the book got its answer, but I can't figure out what the book, or I, did wrong.
: P.S. those are one-eighth and one-seventh x.
: :-)

**********************************
1/8 * x - 1/7 * x = 2, solve for x

x/8 - x/7 = 2

7x - 8x = 112

-x = 112

x = -112

For the book way to be right - the problem must be

1/(8x) - 1/(7x) = 2

7 - 8 = 112 * x

x = -1/112

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