Is it formally right to say that $\Bbb N \subset \Bbb Z$ etc?
60775
Why are integers subset of reals?
21782
Is $\aleph_0 = \mathbb{N}$?
96845
Question: Compare the cardinality between the sets $\Bbb R$ and $\Bbb N^{\Bbb N}$
120642
Let $g : \Bbb N \times \Bbb N \to\Bbb N \times \Bbb N$ defined as $g(m,n) = (m + n,m - n)$
83714
$A \in B$ vs. $A \subset B$ for proofs
55673
Alternate proof that $\exists\ x \in \Bbb{Z}$ such that $ \gcd (a+bx,c) = 1$?
25907
Show $a\Bbb Z+b\Bbb Z = \gcd(a,b)\Bbb Z$
92390
The meaning of notation $\subset\subset$ in complex analysis
70278
$A\subseteq B\to C\setminus B\subseteq C\setminus A\,$ -- how to prove this?
18343
Counting homomorphisms between $\Bbb Z$ and $\Bbb Z_n$ and also between $\Bbb Z_n$ and $\Bbb Q$
89167
Cardinality of equivalence relations in $\mathbb{N}$
72420
Is $\mathbb{N}$ impossible to pin down?
11817
Proving that every set $A \subset \Bbb N$ of size $n$ contains a subset $B \subset A$ with $n | \sum_{b \in B} b$
131983
Prove that $A \subset B$ if and only if $A \setminus B = \emptyset$
31559
If $Z\subseteq Y\subseteq X$ and $Z$ is compact in $Y$, then $Z$ is compact in $X$
63276
Is an arbitrary union of a chain of countable sets countable?
77957
How is $\mathbb N$ actually defined?