I believe the choice A is also correct. Because these involve operations among sets, not numbers. So it doesn't matter if you subtract a certain part twice.

I have a question about a) the subset in general and b) the explanation for question 20. What does a subset mean? In addition, the explanation came up with three possibilities, and I don't quite understand them (like 'in A and B', 'B but not A'.)
Screenshot 2022-11-13 at 20.15.21.png Thanks a lot!

Hi! I don't understand why it's 6 gold pirates and not 7 if there are 7 numbers on the number line...? It's not like the separators a, b, and c will be placed between the numbers, or will they? But I do understand why it's 4 pirates. Thanks!

@RZ923
Yeah! A lot of times in math using ideas in geometry may help, just like the hockey stick identity! You can flip the point of the stick to the other to make it symmetrical.

@spaceblastxy1428 Hi there, since this doesn't give away the solution, I'll answer here. 🙂 The question was written with the intention of not having rotational symmetry. Pretend the chairs are numbered from \(1\) to \(6,\) so that if you rotate a seating arrangement, then it's considered a new arrangement. We can clarify this in the question statement. Thanks for asking!