How do you make a the subject of r equals ab divided by a plus b?

Answer 1

Are you asking to have that equation solved for 'a' ?

r = ab / (a + b)

Multiply each side by (a + b) . . . ra + rb = ab

Subtract 'ra' from each side. . . . rb = ab - ra

Factor the right side . . . . . . . . . rb = a (b - r)

Divide each side by (b - r) . . . . . a = rb / (b - r)