[tex]y= \frac{\ln(\frac{x}{6995}) }{\ln (.85)}[/tex]
Taking the original function, swap the x and y.
y = 6995(.85)^x ----> x = 6995(.85)^y
Solve for y.
Divide both sides by 6995.
x/6995 = (.85)^y
Take the natural log of both sides.
ln (x/6995) = ln (.85)^y
Apply the property of logarithms where log a^b = b log a.
ln (x/6995) = y ln (.85)
Divide both sides by ln (.85) to get y.
y = ( ln ( x / 6995)) / ln (.85)