Question

Another question: r = ab/a+b Find a....

Answer 1

I think the answer is br/b-r = a 

Answer 2

Keep in mind, because they didn't give us any values we can only find what a equals in terms of the other variables. You'll see what I mean after we get to the final answer. 

r = (ab)/(a+b)

Multiply both sides by (a+b)

r(a+b) = (ab)

Divide by r on both sides. 

(a+b) = (ab)/r

Subtract b on both sides. 

a = ((ab)/r) - b 

You can't simplify it any further to my knowledge. Well, besides getting a common denominator with b and subtracting them, but it won't really simplify things. 

Now. Let's get a better answer... haha. Here we go: 

r = (ab)/(a+b) 

Same step. Multiply on both sides. 

r(a+b) = (ab)

This time distribute the r to all values. 

ar + br = (ab)

Subtract ar on both sides. 

ar + br - ar = ab - ar

br = ab - ar

Next step! Factor "a" out of ab - ar by making it a quantity time "a" with "a" removed...
it's easier to show than to explain. So here you go: 

br = a(b - r) 

Divide (b - r) on both sides. 

(br)/(b-r) = a

Hope that helped some! :p