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fractions are killing me, help

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Jason S. | My goal is the success of my students. Knowledge-Patience-HonestyMy goal is the success of my students. K...
4.9 4.9 (115 lesson ratings) (115)
Check Marked as Best Answer
If it's this:
-4/(5x) = 16/15
You can cross-multiply:
-4 * 15 = 5x * 16
-60 = 80x
Divide by 80:
-60/80 = x
x = -3/4
If it's this:
(-4/5)x = 16/15
As stated above by Bill:
Multiply both sides by -5/4.
x = (16/15) (-5/4)
Cancel 16 and the 4.
x = (4/15)(-5/1)
Cancel the 15 and the -5
X = (4/3)(-1/1)
x = -4/3
Notice the answers are reciprocals depending on whether the x is in the numerator or the denominator.
Helpful suggestion:
Please make liberal use of parentheses when posting your questions.
Hope this helps.


Bill W. | Looking for help with Excel, SQL, or other business technology?Looking for help with Excel, SQL, or oth...
4.9 4.9 (36 lesson ratings) (36)
Hi Amy!  As you know, you're trying to solve for x, so you need to isolate the x.  That means moving the -4/5 from the left side over to the right side.
1.  To get rid of the -4/5, you can divide -4/5x by -4/5.  This leaves you with 1x, or simply x.
       -4/5x   =  x
2.  However, whatever you do to one side of the = sign you have to do to the other.  Therefore, since you divided the left side by -4/5, you have to divide the right side by -4/5.  In other words, x = 16/15 divided by -4/5.
3.  Remember the rule for dividing fractions:  Flip the fraction you want to divide by, then multiply the fractions.
       16  รท  -4     =    16  x   5
       15       5            15  x  -4
When you do that math, you'll have the answer for x.  You'll probably want to simplify the result.  Hope this helps!
Bill W.