EDB — 20K

[20K](Solved on 2022-11-24) Having fixed a set $A\subseteq ℝ$ not empty, then $supA$ is the only number $𝛼\in ℝ\cup \{+\infty \}$ which satisfies these two properties

as already seen in [22S]↺↻ for the more general case of totally ordered sets.