What do you do to get rid of subtraction to get rid of subtraction or addition inside of natural logs?

For example,

lna=2

lnb=3

lnc=5

ln(a-4/b^1c^2)=?

I can get it to be:

ln(a-4) - (lnb+2lnc)

Then I get stuck. I don't know what to do with the a-4 in that first log.

The answer to the problem is apparently -21, I don't understand how they got that.

Here is another problem:

lnx + lnx-3 =ln(2x)

x=?

Turns out x=5, but again now idea how they got that.

This is online homework in which showing work is not necessary, but I need to know how to do these problems.

Please help explain how the answers were reached