How do you evaluate ln (1/e)?

It is ##-1##.
We apply the properties of the logarithm:
##ln(1/e)=ln(e^(-1))##
the first property is that the exponent exit and multiply the log
##ln(e^-1)=-ln(e)##
the second property is that the logarithm of the base is 1. The base of the natural logarithm is ##e## then
##-ln(e)=-1##.
In conclusion
##ln(1/e)=-1##.