Rearrange r+s/8s=r-s/8n to make r the subject.

OK, I have started by rearranging the formula:

8n(r+s)=8s(r-s)

What do I do next?

so you must have meant

(r+s)/(8s)=(r-s)/(8n)

so 8n(r+s)=8s(r-s) is correct so far. Le'ts expand it
8nr + 8rs = 8rs - 8s^2
8nr = -8s^2
nr = -s^2
r = -s^2/n

thank you!

just realised, should the second line be

8nr+8NS?, not 8rs?

just realised, should the second line be

8nr+8NS?, not 8rs?.........

your are right, good for you to notice

I have to mind my n, r and s's

8nr + 8ns = 8rs - 8s^2
collect all terms containing r to one side
8nr - 8rs = -8s^2 - 8ns
factor out the r
r(8n - 8s) = -8s^2 - 8ns
r = (-8s^2 - 8ns)/(8n - 8s)
divide top and bottom by 8 on the RS
r = (-s^2 - ns)/(n-s)
or -s(s+n)/(n-s)

great, that makes sense, thanks

To make r the subject of the formula, we need to isolate it on one side of the equation.

Next, we can distribute the terms on both sides of the equation:

8nr + 8ns = 8sr - 8s

Now, let's simplify the equation further by grouping the terms with r on one side:

8nr - 8sr = -8s - 8ns

Factor out r from the terms with r:

r(8n - 8s) = -8s - 8ns

To isolate r, divide both sides of the equation by (8n - 8s):

r = (-8s - 8ns) / (8n - 8s)

And there you have it! r is now the subject of the formula.