1. ## rewrite log expression

Hello, we rewrote this log expression:
ln6 - ln15 + ln20

to become
ln(6/15 + 20)
which was simplified to:
ln(2/3 + 4)
and which then:
= ln 8.

The problem is I cant see how the last step occurred eg. ln(2/3 + 4) becoming ln 8.
Thank you for any help in understanding this step.

2. Originally Posted by fran1942
Hello, we rewrote this log expression:
ln6 - ln15 + ln20

to become
ln(6/15 + 20) no ... ln(6/15 * 20)
...

3. lna+lnb=ln(ab)
lna-lnb=ln(a/b)

So the given one is ln6-ln15+ln20=ln120-ln15=ln(120/15)=ln8