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March 6, 2015

March 6, 2015

Posted by **mary** on Friday, April 22, 2011 at 7:55pm.

I can't decide if I should cross multiply by -20 or just 20. The - is in the middle of the x and 20 (like a fraction)

I came up with 2 possible answers:

x=40/49 and x = 40/47

- algebra -
**Damon**, Friday, April 22, 2011 at 8:04pmscroll down, I answered

- algebra -
**Imagine**, Friday, April 22, 2011 at 8:05pmThe answer I got using a calc is 2

- sign error -
**Damon**, Friday, April 22, 2011 at 8:15pm(-12x+10)(-20)/5 = -x (-20/20)

I made a sign error here

48 x -40 = +x

47 x = 40

x = 40/47

- no way I get 2 -
**Damon**, Friday, April 22, 2011 at 8:16pmNot for this problem

- algebra -
**MattsRiceBowl**, Friday, April 22, 2011 at 8:39pmIs it (-12x+10) / 5

Or

-12x + (10/5)

?

- algebra -
**Damon**, Friday, April 22, 2011 at 8:51pmscroll down Matts. I did it both ways.

- algebra -
**Damon**, Friday, April 22, 2011 at 8:53pmI am not a big fan of the expression "cross multiply"

What you want to do here is multiply both sides, all terms by -20 (or 20 would work too)

FIRST THE WAY YOU TYPED IT (probably wrong)

-12(-20) x + 2(-20 ) = -x(-20)

240 x - 40 = 20 x

220 x = 40

x = 2/11

NOW WHAT I THINK YOU MEAN

(-12x+10)(-20)/5 = -x (-20/20)

48 x -40 = -x

49 x = 40

x = 40/49

PARENTHESES ARE IMPORTANT WHEN TYPING EQUATION ON A COMPUTER (because of order of operations)

typo - Damon, Friday, April 22, 2011 at 8:14pm

(-12x+10)(-20)/5 = -x (-20/20)

I made a sign error here

48 x -40 = +x

47 x = 40

x = 40/47

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