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# Algebra Help (Chances are theres at least one of you that cn help me)

The worst thing in the world is Algebra, I suck at any and all math and I am terrified of the next couple of months with it for my college courses. I have asked my Professor, but she is taking a long time to answer, so hoping for some clarity.

Linear Equations
Solve: 1/2x - 1/6x = 5

6(1/2x -1/6x) = 5 * 6
3x - x = 3
2x = 30
x=15.
ok so I get the process of multiplying in the parenthesis (PEMDAS)etc., but what I do NOT understand is WHERE they get the 6 all of a sudden. Where did they figure to multiply everything with the 6? I am SO confused on that. is it a Greatest Common Multiple or something?

Oh btw this was a sample equation during the online lecture, not something I figured out for myself

Asked by Anonymous at 9:29 PM on Mar. 25, 2013 in

This question is closed.
Answers (15)
• "ok, but how did you figure to use 6?"
"so you use the Lowest common denominator, not the Greatest common factor?"

Don't let terminology get you confused here. You are trying to turn the messy fractions into easy whole numbers that you can subtract, right? So the question is: what do I have to multiply these fractions by to get both of them to be whole numbers? So just think... 1/2 * what = a whole number? 2, 4, 6, 8, 10, 12... etc. Right? Now, which ones of these * 1/6 also equals a whole number? 6 and 12 (and any other multiple of 6) right? So in this example, they chose the smallest number that you can multiply to both fractions in order to get whole numbers, or 6. By the way, you could also get the same answer by using 12 instead - you would just have to simplify a little more. Does that make sense?

Answer by Sebbiemama at 10:15 PM on Mar. 25, 2013

• You have to get rid of the 1/6 and 1/2, easiest way to do that is multiply by 6.

6*1/6=1 and 6*1/2=3

Answer by kmath at 9:33 PM on Mar. 25, 2013

• because 6 works for both numbers

Answer by feralxat at 9:37 PM on Mar. 25, 2013

• 6 is the lowest common denominator for both numbers.

Answer by kmath at 9:44 PM on Mar. 25, 2013

• ok, but how did you figure to use 6?

Comment by Anonymous (original poster) at 9:34 PM on Mar. 25, 2013

• That's where I was confused, so you use the Lowest common denominator, not the Greatest common factor? I am so terrible at this

Comment by Anonymous (original poster) at 9:46 PM on Mar. 25, 2013

• the lowest common multiple

Comment by Anonymous (original poster) at 9:49 PM on Mar. 25, 2013

• x=15.......... go here.   http://www.algebra.com/services/rendering/simplifier.mpl

Answer by chrstny88 at 10:02 PM on Mar. 25, 2013

• Oh, and you don't have to start with 1/2. You could also start with "what * 1/6 = a whole number" and then apply it to the 1/2.

And the number in the numerator isn't that important at this point... just getting rid of the fractions. So if the problem was:
1/2x - 1/3x = 5
1/2x - 2/6x = 5
6(1/2x - 2/6x) = 6*5
3x - 2x = 30
x = 30

Hope this helps.

Answer by Sebbiemama at 10:23 PM on Mar. 25, 2013

• its not 30... am i the only one that looked it up on more then one algebra site??? the answer is x=15.. op has it right.

Answer by chrstny88 at 11:58 PM on Mar. 25, 2013