Answer:
part of the large bowl of popcorn.
Explanation:
If Nathalie's brother takes
of the large bowl of popcorn for himself, then there remain
of the large bowl of popcorn.
Now, this amount of popcorn is shared among Nathalie and her three friends.
If each of them get the same amount of popcorn then each of then will get
part of the large bowl of popcorn. (Answer)