This riddle has been around for some time on internet platforms such as Instagram, Facebook, and WhatsApp, and many people still argue over what the answer might be, as there are many possibilities. The correct answer is The advice was to add his horse to the group of horses, to make a total of 18 horses. The oldest son will get half – 9 horses. The middle son will get one third – 6 horses The youngest son will get one ninth – 2 horses There is now 1 remaining horse which belongs to the traveling mathematician.