Making x the subject

[livy91]

Hi

I am currently doing some past papers for my GCSEs and i can never answer these could so can anyone help?

the question is:

make x the subject of
w= (x/2) + 3


thank-you

xxx

[StuartS]

w=(x/2) +3

subtract 3 from both sides

so w-3 = (x/2) + 3 -3

which leaves

w-3 = x/2

Now multiply both sides by 2

2(w-3) = 2 (x/2)

the 2's cancel in 2(x/2) to give x

so

x=2(w-3)

I hope that helps

[The Prince]

I did it a different way. I got a different answer. I'm not sure which one of ours is correct.

w = (x ÷ 2) + 3

w + ½x = x + 3

(w + ½x) – 3 = x

It's interesting.

(w + ½x) - 3 = x and x = 2w - 6 are both true and this is proved because ½x = w - 3 because if you double w - 3 it makes 2w - 6 and since ½x is equal to w - 3 then adding ½x to w - 3 does make it so

(w + ½x) - 3 = 2w - 6 and since

2w - 6 = x then (w + ½x) - 3 is an alternative way of expressing x.

Sorry, I rambled. :P

[ExamSolutions]

StuartS is correct.

In your version, you have the subject x on both sides of the equals sign.

The object of rearranging a formula is to have the subject only on one side.