Actually, you're right, thank you!
The catch here is that we came to different answers through different methods, but
both are correct because of the constant that is being ignored.
ln(5 - i) = ln(15 - 3i) - ln(3)
And ln(3) is of course a constant.
(I used a lowercase i for legibility)
Kind of ashamed I missed that, I used to grade math papers...