The king added his horse to the 11 horses in the stable. The oldest
child then got
or 6 horses. The middle child got
or 3 horses, and the youngest child got
or 2 horses. Since 6 + 3 + 2 = 11, the king kept his own horse.
Extension:
Using
18 horses, the children would receive 8, 6, and 3 horses respectively.