I was having trouble with this question and wondered if I could get some help with it ?

How many terms of the geometric series + ... must be taken so that the sum differs from 3 by less than ?

I started with this inequality:

and ended up with this:

Of course you cannot take the log of a negative number so how do I work out what n must be greater than? Also sorry I have no idea how to do that maths code thing so it might look a bit messy, Thanks