I worked on this a bit. Could someone confirm if my method is correct?

-71=58log[(5/125) + (b120/b12)]

I simplified the equation to:

-1.22 = log [(5/125) + (b120/b12)]

10^-1.22 = (5/125) (b120/b12)

0.06 - 0.04 = b120/b12

0.02 = ratio of b120/b12

I don't if you can simplified for value of b.

Any suggestions?