I understand how to do this with e or ln but not a log

They work the same way as each other ...

You can express exponential equations using logarithms and vice versa:

log_{b}(expression) = number ... means the same thing as b^{number} = (expression).

What I tell my students is to remember to keep the bases the same, and the exponent of the base stands alone in the logarithmic expression.

Example: log_{5}(25) = 2 means the same thing as 5^{2} = 25

With natural logarithms (where the base is an understood ** e**), you do the same thing...

Example: ln (4) = 1.3863 means the same thing as **e**^{1.3863} = 4

Hope this helps you.