transpose D=15log(pont/pin) change subject to pin

Assuming that you are using natural logs here, the only issue here is to remember that if a = ln(b), then e^a =b:


D = 15 ln(\frac {pont} {pin}) \\
\frac D {15} = ln (\frac {pont} {pin} ) \\
e^{(D/15)} = \frac {pont} {pin} \\
pin = \frac {pont} {e^{(D/15)} }= pont \ \times \ e^ {(-D/15)}

A side note ebaines:

I think that it was P_in and P_out :)

P_{in} P_{out}

A side note ebaines:

I think that it was P_in and P_out :)

P_{in} P_{out}

Perhaps it was - although in that case the OP misspelled P_out, twice...