Explanation

This question is made confusing by the fact that the clubs are numbered, creating a profusion of irrelevant digits in the question. Let's call the clubs Th, F, and S, for the first letters of thirty, fifty, and sixty. Also, since we are talking about the overlap of group memberships, we are in Venn diagram territory. Let's sketch it out and fill in what we can:



We could find FS, as we are being asked, by getting T. And there might be another way to find it, as well, though we are missing a lot of information. Let's look at the data statements, starting separately.

Statement (1) tells us the number of members in the first club. In other words, . That allows us to calculate T, from which we can calculate FS. So Statement (1) is sufficient.

Statement (2), in terms of the diagram, tells us the number of members of the bottom circle, S, outside of the portion we are looking for. The members of F are 60% of the total, so the non-members of F are 40% of the total, or 0.4T, and 25% of that amount is 0.1T. The problem is that this statement doesn't help us know T. It gets us closer to the total membership of S, but we're not even looking for that. We can see in analysis by cases: we can imagine that T is small or very large. Both are permitted by the data and lead to different answers for the overlap of F and S. Therefore, Statement (2) is insufficient.

The correct answer is (A).