p : ℕ → Prop
inst✝ : DecidablePred p
n : ℕ
⊢ Cardinal.mk { k // k < n ∧ p k } ≤ Cardinal.mk ↑{k | p k}
p : ℕ → Prop
inst✝ : DecidablePred p
n : ℕ
⊢ ↑(count p n) ≤ Cardinal.mk ↑{k | p k}
rw [count_eq_card_fintype, ← Cardinal.mk_fintype]
no goals
p : ℕ → Prop
inst✝ : DecidablePred p
n : ℕ
⊢ Cardinal.mk { k // k < n ∧ p k } ≤ Cardinal.mk ↑{k | p k}
exact Cardinal.mk_subtype_mono fun x hx ↦ hx.2