Well-Ordered Subset
From ProofWiki
Theorem
Let $R$ strictly well-order $A$ and $B \subseteq A$. Then $R$ strictly well-orders $B$.
Proof
By Foundational Relation Subset, $R$ is a foundational relation on $B$.
By Totally Ordered Subset, $R$ totally orders $B$.
By the above two statements, $R$ well-orders $B$. $\blacksquare$