2005 BMO2 showing that at least three different sets in the list are subsets of at least four sets in X.
5118
Show that $n ≤ 100$ if $ \{A_1,A_2,... ,A_n\}$ is a set of distinct $3$-element subsets of $\{1, 2,... , 36\}$ such that...
51617
What is the proof that the total number of subsets of a set is $2^n$?
146098
Number of nonempty subsets of a set with $n$ elements
49147
Showing that the class of all sets of a particular cardinality is not a set.
83518
Proving Two sets have same cardinality
11817
Proving that every set $A \subset \Bbb N$ of size $n$ contains a subset $B \subset A$ with $n | \sum_{b \in B} b$
93771
Prove that for any set $A$ there is some $x \notin A$
105886
A question on the proof of 14 distinct sets can be formed by complementation and closure
9850
How many ways are there to choose 3 subsets $A,B,C$ of a set $\{1,2,3...n\}$ such that $ A \cap B \cap C = \emptyset $
142583
Subsets of the Cantor set
113922
Proof that the intersection of any finite number of convex sets is a convex set
152342
$x_1+x_2+\cdots+x_n\leq M$: Cardinality of Solution Set is $C(M+n, n)$
146204
Subsets sharing at most $i$ elements
1627
Cartesian product of an arbitrary number of sets
103769
The Cartesian product of a finite number of countable sets is countable
111324
Finding number of relations on a set with 3 elements
65978
How many subsets does the set $\{1, 2, \dots , n\}$ have that contain no two consecutive integers if $1$ and $n$ also count as consecutive?