How to find one value in terms of other variables?

[Eddie10]

Homework Statement

I need to find q in terms of f and p.

Homework Equations

I am dealing with this equation at the moment:
1/p + 1/q = 1/f.

The Attempt at a Solution

I think I should isolate the q, so that I have the variables p and f on one side of the equals sign, and q on the other side of the equals sign.

Am I correct in thinking this?

 

[ehild]

Yes.

 

[Eddie10]

My results:

1/q =(1/f) - (1/p)

1/q= (p-f)/(pf)

q= pf/(p-f)

Are they correct?

 

[ehild]

Yes.