proposition: Lemma le_2_4 : 2 ≤ 4.
proof: Proof. apply (order_preserving (1+)), le_1_3. Qed.
imports: Coq.setoid_ring.Ring MathClasses.interfaces.abstract_algebra MathClasses.interfaces.orders MathClasses.theory.rings MathClasses.orders.orders MathClasses.orders.maps