+118724 Log of what base 5?
log of 20 base 5 can be written using LaTex as log_{5}20 $$log_{5}20$$ see 
To enter it into this calc enter log(20,5) $${{log}}_{{\mathtt{5}}}{\left({\mathtt{20}}\right)} = {\mathtt{1.861\: \!353\: \!116\: \!146\: \!786\: \!2}}$$ see again 
