Question 20605
You could use natural logs (logs to the base e).

{{{6^(1-x) = e}}} Take the ln of both sides.
{{{(1-x)ln(6) = ln(e)}}} But ln(e) = 1, so
{{{(1-x)ln(6) = 1}}} Divide both sides by ln(6)
{{{1-x = 1/ln(6)}}}
{{{x = 1 - (1/ln(6))}}} Use your calculator to find ln(6).
{{{x = 1 - 0.558}}}
{{{x = 0.442}}}