This book contains the most interesting problems from the first 24 years of the 'Mathematical Duel', an annual international mathematics competition between the students of four schools: the Gymn zium Mikul se Kopern ka in B lovec, Czech Republic, the Akademicki Zesp l Szk l Og lnoksztalcących in Chorz w, Poland, the Bundesrealgymnasium Kepler in Graz, Austria and the Gymn zium Jakuba Skody in Přerov, Czech Republic.The problems are presented...