A finite set such that $x*y=x*z \implies y=z$ and $y*x=z*x\implies y=z$
62286
Suppose $G$ is a semigroup and it holds both left and right cancellation.
116527
Validating a proof for necessary and sufficient conditions on sets A & B such that $P(A) \cup P(B) = P(A\cup B)$
70143
Mutually exclusive countable subsets of a countable set
106756
Union and Intersection of Sets $A_{i}$ and $B_{j}$
59813
Prove that for all sets A and B, A ∩ B = ∅ implies ( A ∪ B ) - B = A
80180
Discrete and compact subset must be finite
123613
Double Complement of a set proof
77791
Proving an inclusion related to algebraic sets and interpreting it
158882
Prove the existence of some weird family of sets
145873
Let $X$ and $Y$ be finite sets. Then the set $Y^X$ is finite and $\#(Y^X) = (\#Y)^{\#X}$.
140868
Axiomatization of $\mathbb{Z}$ via well-ordering of positives.
136835
ZF Set Theory - If $|A|^{|B|} = |B|$, then $|A| = 1 = |B|.$
31389
consistency of ZF\{Power Set axiom}
30587
Uncountable well ordered set in $Z^-$ theory.
62936
Proving equivalencies of two versions of the Axiom of Choice
95244
Prove that a finite union of closed sets is also closed
85819
A non-polyhedral pair $(X,A)$ with both $X$ and $A$ polyhedral