If $A\subseteq \{ 1, 2, ... 2n \}$ has $n+1$ elements, then it contains $a$, $b$ such that $a\mid b$
75852
Using Pigeonhole Principle to prove two numbers in a subset of $[2n]$ divide each other
20335
If $A\subset B$ then $\bar{A}\subset \bar{B}$
76405
Let n be an even integer. How many different ways can I choose subsets of the set {1,2...,n}
104855
Prove that $N \subset Z(G)$
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?
43979
The total number of subsets is $2^n$ for $n$ elements
56399
Proof for $A \cup B = B$ if and only if $A \subset B$
19396
For subspaces, if $N\subseteq M_1\cup\cdots\cup M_k$, then $N\subseteq M_i$ for some $i$?
99782
$a_{n+1}=|a_n|-a_{n-1} \implies a_n \; \text{is periodic}$
41080
If A, B, and C are set and $A \subset B ,B \subset C \rightarrow A \subset C$
140668
Union of $2$ set $A, B$ where $ A$ is a subset of $B$
134921
Find the number of all subsets of $\{1, 2, \ldots,2015\}$ with $n$ elements such that the sum of the elements in the subset is divisible by 5
46286
Prove if $a\mid b$ and $b\mid a$, then $|a|=|b|$ , $a, b$ are integers.
60309
Let X be a subset of {1,2,...,2014}...
47434
Proof that $A \subseteq B \Leftrightarrow A \cup B = B$
11967
number of subsets of even and odd
44897
Proof: If $n=ab$ then $2^a-1 \mid 2^n-1$