britney is on her high school track team.
this year she placed first in four of her races, second in six of her races, and third in eight of her races.

왜 four races 라고 안 하고 four of her races 라고 하죠?
문법적으로 어떻게 그렇게 되는지 전혀 모르겠어요.

쉽게 설명해 주세요 ~~~ㅜ