consider
a^x = b
(write it on paper)
we can make b the subject, which is above
we can make a the subject, which will be: a = b^(1/x)
however, to make x the subject there is a notation: logs
so x is the power by which we raise a to get b.
the notation is logab=x
note: the a is subscript
So make 5^x the subject first
so assuming u got 5^x = s, where s is a number
so x is the power by which we raise 5 to get s
ie x=log5s
Now u can use an advanced calculator