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- Feb 5, 2013

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3x = 15

x = 15/3

x = 5

x = 15/3

x = 5

- Jan 29, 2012

- 1,151

This makes no sense! In the first place, what does it mean to divide by anCan anyone please help me with this equation 3x =15

My workings ;3x=15

Any help is appreciated, thanks

= 5x, as 15 divide by 3x=5x

In the second place, 3x is NOT equal to 5x unless x= 0. There is nothing here that says either x= 0 or 3x= 5x.

To "solve for x" means to get x by itself: "x= something".

In the original equation, 3x= 15, x is not "by itself" because it is multiplied by 3. To get x "by itself" we need to "undo" that- and we undo "multiply by 3" by dividing by 3. And, of course, anything we do to one side of the equation we must do to the other.

Rather than "15 divided by 3x= 5x" you should have said "15 divided by 3 is 5".

Dividing both sides of 3x= 15 by 3 gives

(3x)/3= 15/3

x= 5.

- Oct 15, 2015

- 40

\(\displaystyle \dfrac{x-1}{6}=\dfrac{1}{3}\)

\(\displaystyle \dfrac{x}{6}=\dfrac{2}{3}\)

\(\displaystyle x = \dfrac{2}{3} \cdot 6 = 4\)

When I pressed him on what he did, he said "in the second step I added one to the numerator of both sides of the equation and anything I do to one side of an equation must be done to the other side of the equation ... which is what you said ... so it must be correct."

- Jan 29, 2012

- 1,151