The total number of copies is 17, 9 copies are 9 heads, 6 copies are 6 heads and 2 copies are 2 heads.

This is the grade of grade six.

decimal

1/2+ 1/3+ 1/9= 17/ 18

Three people just got 17 heads. Only by borrowing a person's head can you score points, and you still have to return what you borrowed to others.