So there are 18 camels.

The eldest son 1/2 points 9 heads.

The second son 1/3 points and 6 heads.

The youngest son 1/9 points and 2 heads.

There is a mathematical story. An old man with 17 camels left a puzzling last word for a son: half of the camels were given to the eldest son, one third to the second son and one ninth to the younger son, but it was not allowed to slaughter camels when distributing them. Just as the three sons had no good plans, a philosopher riding a camel came. After he knew the contents of his last words, he classified his camels as a group of camels, so there were 18 camels. The sons divided 9 camels, 6 camels and 2 camels according to their father's will, which is also 17 camels. The philosopher retrieved his camel. The three sons in the story stare at 17 camel, bound by straight thinking. Philosophers open up traffic wisdom, and the word "borrow" makes the problem known to the world and solved it easily.