. apply round_le_trunc_of_le_trunc npos hfaithful₀ hfaithful₁
  exact Nat.le_trans tsub_le_self hfa.ge
a n : ℕ
round : ℕ → ℕ
npos : 0 < n
hfaithful₀ : faithful₀ n round
hfaithful₁ : faithful₁ n round
b : ℕ
hfa : trunc n a = a
⊢ round (a - b) ≤ trunc n a

a n : ℕ
round : ℕ → ℕ
npos : 0 < n
hfaithful₀ : faithful₀ n round
hfaithful₁ : faithful₁ n round
b : ℕ
hfa : trunc n a = a
⊢ trunc n a ≤ a
a n : ℕ
round : ℕ → ℕ
npos : 0 < n
hfaithful₀ : faithful₀ n round
hfaithful₁ : faithful₁ n round
b : ℕ
hfa : trunc n a = a
⊢ trunc n a ≤ a