Question

Solve for L: d=LM/r2+r1

Answer 1

d = LM / (r2 + r1)....multiply both sides by (r2 + r1)
d(r2 + r1) = LM....distribute
dr2 + dr1 = LM...now divide both sides by M
(dr2 + dr1) / M = L

Answer 2

In order to solve for L, the first thing to do in the equation d=LM/r2+r1 is to multiply (r2+r1) to both sides to remove the fraction. This would result in this:
d(r2+r1)=LM

Now that you just have LM left on one side, to isolate L, you must divide both sides by M to get your answer as L=d(r2+r1)/M.