Sharing Cattles

Sharing Cattles puzzle
A man passed away leaving 18 cattles for his 3 sons in his will. He directed that the 1st son should have half of all the cattles, the 2nd should have one-third of all the cattles & the 3rd should have one-ninth of all the cattles.

How many cattles will each of the sons have, if no cattle must be killed or cut?

Half=18/2=9, 1/3rd =18/3=6, 1/9th=18/9=2. 2+6+9=17.