intuition.
rewrite <- ratSubtract_ratAdd_assoc.
eapply ratSubtract_ratAdd_inverse.
apply bleRat_total.
case_eq (bleRat r1 r2); intuition.
Qed.

(* Specifications: *)
Lemma rat_ge_1 : forall n (d : posnat),
n >= d ->
1 <= RatIntro n d.