Question 371552
How do you solve this formula for c?

A = cd over c + d

A = cd/(c+d)
Cross multiply
A(c+d) = cd
Ac+Ad = cd
Subtract cd from both sides
Ac-cd+Ad = 0
Subtract AD from both sides
Ac-cd+Ad-Ad = 0 - Ad
c(A-d)      = -Ad
Divide both sides by (A-d)
        c   = -Ad/(A-d)