For me it's 576 since it is the smallest amount of people watching the said movies.
There are possibilites that these 576 people belong to 1,342 people who are watching action movies. Same with those who are watching comedy movies, there's this possibilites that these 576 people does belong to 890 people.
In my opinion, you can't add the three of them to find the answer. Because the question is How many are watching three movies (possibility: watching three movies at the same time) so the least is my answer.