Question 196668
I'm assuming that the default base of each log is 10.



{{{log(10,(8))+log(10,(5))-log(10,(4))}}} Start with the given expression.



{{{log(10,(8*5))-log(10,(4))}}} Combine the logs using the identity {{{log(b,(A))+log(b,(B))=log(b,(A*B))}}} 



{{{log(10,(40))-log(10,(4))}}} Multiply



{{{log(10,(40/4))}}} Combine the logs using the identity {{{log(b,(A))-log(b,(B))=log(b,(A/B))}}}



{{{log(10,(10))}}} Reduce



{{{1}}} Evaluate the log base 10 of 10 to get 1



So {{{log(10,(8))+log(10,(5))-log(10,(4))=1}}}