solve for g. R=(g*s)/(g+s)

Answer 1

invert and separate terms ... 1 / R = [g / (g*s)] + [s / (g*s)]

1 / R = (1 / s) + (1 / g) ... 1 / g = (1 / R) - (1 / s) = [s / (R*s)] - [R / (R*s)]

1 / g = (s - R) / (R*s) ... g = (R*s) / (s - R)

Answer 2

R=(g*s)/(g+s)
R(g+s) = gs
Rg+Rs = gs
g(s-R) = Rs
g = Rs/(s-R)