y =

ln(

x / m

- sa) / r²

First, let's get rid of the denominator
multiplying both sides by r²

r²y =

ln(

x / m

- sa)r² / r²

          r²y = ln(

x / m

- sa)

To get rid of the natural log, we'll employ e

e^yr2 = e ln(

x / m

- sa)          e^rry =

x / m

- as

Lastly, we'll multiply both sides by m

me^rry =

xm / m

- asm          me^rry = x-mas