Question 749112
Natural Log has base e, so you'll raise e to both sides of the equation:

{{{ln (5-x) =12}}}

{{{e^(ln (5-x)) = e^12}}}

The e and ln basically cancel each other out, so you've got:

{{{5-x = e^12}}}

Now just solve for x:

{{{5-x = e^12}}}

Add x to both sides:

{{{5 = e^12+x}}}

Subtract e^12 from both sides:

{{{5-e^12 = x}}}

That is an exact answer.  If you want an approximated answer, just evaluate that and round to whichever place you need to.