Theorem oldno

Description: An element of an old set is a surreal. (Contributed by Scott Fenton, 27-Feb-2026)

	Ref	Expression
Assertion	oldno	$$⊢A\in \mathrm{Old}\left(B\right)\to A\in \mathrm{No}$$

Proof

Step	Hyp	Ref	Expression
1		oldssno	$$⊢\mathrm{Old}\left(B\right)\subseteq \mathrm{No}$$
2	1	sseli	$$⊢A\in \mathrm{Old}\left(B\right)\to A\in \mathrm{No}$$