1/M +1/N = 1/P for P
\( \frac{1}{M} +\frac{1}{N} = \frac{1}{P} \;\;find\;\;P \\ \frac{N}{MN} +\frac{M}{NM} = \frac{1}{P}\\ \frac{N+M}{MN} = \frac{1}{P}\\ \frac{MN}{N+M} = \frac{P}{1}\\ P=\frac{MN}{N+M} \)
