Example to disprove If $A\subseteq B$ and $B$ is denumerable, then $A$ is denumerable I want to see if my counterexample is valid: Let $A=\\{5,6,7\\}$ and $B= \mathbb{N}$ Then, $B$ is denumerable, but $A$ is not. ...--prophetes.ai

Example to disprove If $A\subseteq B$ and $B$ is denumerable, then $A$ is denumerable I want to see if my counterexample is valid: Let $A=\\{5,6,7\\}$ and $B= \mathbb{N}$ Then, $B$ is denumerable, but $A$ is not. My definition of denumerable is equivalence to $\Bbb{N}$. My definition of countable is finite or denumerable.

Yes, that is a counterexample!