Or, after a rancher's death his 3 sons are dividing up his herd of 17 horses. According to his will, the first son get 1/2the herd, the second gets 1/3 and the third son gets 1/9.
After arguing how to divide 17 by 1/2, 1/3 and 1/9 a neighbor rides up and, being a long time friend, puts his horse in with the other 17. That makes 18 horses in the corral, so 1/2 = 9, 1/3 = 6 and 1/9 = 2. Therefore being that 9+6+2 = 17 the neighbor takes his horseout of the corral and rides back home.