rattac.
eapply (@mult_le_compat_r_iff x1); trivial.
rewrite <- mult_assoc.
rewrite (mult_comm x).
rewrite mult_assoc.
eapply le_trans.
eapply mult_le_compat.
eapply l.
eauto.
repeat rewrite <- mult_assoc.
repeat rewrite (mult_comm x0).
repeat rewrite mult_assoc.
eapply mult_le_compat; eauto.
Qed.

Theorem eqRat_impl_leRat : forall r1 r2,
eqRat r1 r2 ->
leRat r1 r2.