# Math Help - solve for x problem

1. ## solve for x problem

stuck on this on

$s = a / l-r$

solve for r

also how do you make a divide a straight line in this forum?

2. multiply both sides by l - r

s(l - r) = a
sl - sr = a

rearrange
sl - a = sr

sr = sl - a

divide both sides by s

r = l -a/s

I think

3. Originally Posted by Joel

multiply both sides by l - r

s(l - r) = a
sl - sr = a

rearrange
sl - a = sr

sr = sl - a

divide both sides by s

r = l -a/s

I think

s = a
divide
1 - r

4. Originally Posted by realistic
s = a
divide
1 - r
Huh?

Do you mean s = a / (l - r)
What you posted means s = (a/l) minus r

5. Originally Posted by Wilmer
Huh?

Do you mean s = a / (l - r)
yeah this

like i had in original post

6. Originally Posted by realistic
yeah this

like i had in original post
Ok; so a = l(s + r)
a = ls + lr
Can you not finish it?

7. Originally Posted by Wilmer
Ok; so a = l(s + r)
a = ls + lr
Can you not finish it?
the answer is r = s-a/s In the book i have

anyone know how to get this answer ?

8. Originally Posted by realistic
the answer is r = s-a/s In the book i have

anyone know how to get this answer ?
If you learn to use the LaTex markup tags and that will help make things more clear in the future. You would enter \frac{a}{1-r} between the "math" tags.

Anyway,

$s= \frac{a}{1-r}$

Multiply both sides by 1-r

$s(1-r) = a$

Use distributive law

$s - sr = a$

Subtract both sides by s

$-sr = a - s$

Almost there, now divide both sides by -s (minus s)

$r = \frac{a - s}{-s}$

All the cool kids move the negative sign up from the denominator

$r = \frac{-(a - s)}{s}$

Distributing the minus sign (which is really a -1)

$r = \frac{-a + s}{s}$

Now rearranging the numerator so the positive term comes first

$r = \frac{ s - a}{s}$

9. ok thanks i see now