how do i set up a broadcast fax for my small business with an opt out number.
I need to broadcast to only about 100number initially but i need to
know how to get an automatic opt out number so i dont need to take
each opt out call personally

Unless you have received specific consent from each owner of each fax
machine, then broadcast faxes are illegal and you may be fined over
$100,000 for sending out 100 faxes.  I know this doesn't answer your
question, but wanted to make sure you were aware of the law based on
your stated intentions.

This is not my area of expertise, but I believe the laws related to
faxing vary from place to place. I doubt that much useful information
can be provided without knowing where the questioner is located. We
don't need an address, of course, but knowing what nation (and what
state or province within that nation) would certainly be helpful.

If it is illegal to send faxes with an opt out number than why do we
get 20-30 per day.

In the US, if you receive a junk fax (business fax that you did not
give your consent to receive), then under the junk fax laws, you may
bring suit against the sender.  This does not deter some senders
because they are either unaware of the law, or aware that it is
difficult and time consuming to pursue and thus do not care.  There
are some companies that I have recently read about that receive so
many junk faxes that they have decided to pursue each one in court and
have won thousands of dollars in judgements so far.

I was afraid of that I think they know the law and they know i wont
sue for the cost of my toner