intros.
eapply leRat_trans.
2:{
eapply eqRat_impl_leRat.
apply ratAdd_comm.
}
apply ratAdd_any_leRat_l; eauto.
Qed.

Lemma ratAdd_eq_impl_leRat_l : forall r1 r2 r3,
r1 == r2 + r3 ->
r2 <= r1.