Question 744569
I'm not sure about what the problem really is, so I'll solve two guesses. Maybe one of them is wahat you wanted,
 
IF IT IS A BASE 3 LOG:
{{{243=81*3=3^4*3=3^5}}}
so {{{log(3,243)=5}}}
 
IF IT IS JUST THE COMMON (BASE 10) LOG OF A PRODUCT:
{{{log((3*243))=log((3^5))=5*log(3)}}}