Maths
posted by Sarah .
Hey :)
I'm sitting my maths noncalculator GCSE tomorrow and am currently revising. I'm doing a practise paper and am currently stuck on this question:
Express A in terms of w.
3w + 20 A
 = 
200 A + 12
 What does the question mean?
 Can you explain to me step by step how to solve this problem? I'm really bad with understanding maths lingo btw :)
Thank you!

Arg, that problem is supposed to be
3w + 20

200
is equal to
A

A + 12 
write it like this, it is easier to read in this format.
(3w+20)/200 = A/(A+12)
crossmultiply to get
(3w+20)(A+12) = 200A
3Aw + 36w + 20A + 240 = 200A
3Aw  180A = 240  36w
switch all the signs
180A  3Aw = 240 + 36w
factor out an A
A(180  3w) = 240 + 36w
divide by 180  3w
A = (240+36w)/(1803w)
A = (80+12w)/(60w)