How To Clear System and administrator password have been setted to Bois ?

You need to place a voice phone call to Dell support.  Be prepared to verify your ownership details before they'll assist.

please i dont have international phone i can only make local phone call and i am in egypt right now

There is just one way to clear the password easily - by calling Dell as noted.  If you cannot or will not do that, there's just one other way - replace the mainboard.  That will cost you $300+ -- an international phone call will be less expensive.