Software for acounting
 

Hello

Can you help me find a software for the acounting for a small business? Something like lets me add prices and then do math operations with them easily and it can be used by old people who doesn't know about computers.

The link below goes to a page with a couple of options, GnuCash probably the more well known which you should be able to install from your distribution repositories. Can't give and more detail as you neglected to mention which Linux distribution if any, you are using.

http://www.followtheflow.org/accounting/

I think that I'd buy Quicken® ... and if necessary, a Windows box on which to run it. (Or AccountEdge® for a Mac.)

I frankly wouldn't make "Linux" the ruling-constraint here. Find the most appropriate software for the application, then purchase a computer of an appropriate configuration in which to run it. If that computer is dedicated just to that particular task, then so be it. Computers are cheap now, and a used one will do nicely.

If you are looking for Linux accounting software, you may want to try Stansoft http://www.stansoft.org.

If you want something free, Gnucash is powerful enough for a small business. Any accounting software will take some time to learn, but even an accountophobe like me can manage it. (And just because your old doesn't mean you're stupid: I'm 69 and studying philosophy.) Have a look at the documentation:
http://www.gnucash.org/docs.phtml

If they are using an outside accountant to do things like their taxes, then you really want to talk to that accountant first. Most accountants understand and use Quickbooks and will likely charge extra if they have to import data from another source (if they can do it at all).