intro (_ : n + m₁ ≤ n + m₂)
ℕ : Type
inst✝³ : Core ℕ
inst✝² : Induction ℕ
inst✝¹ : Addition ℕ
inst✝ : Sign ℕ
order_inst : Order ℕ
n m₁ m₂ : ℕ
⊢ n + m₁ ≤ n + m₂ → m₁ ≤ m₂
ℕ : Type
inst✝³ : Core ℕ
inst✝² : Induction ℕ
inst✝¹ : Addition ℕ
inst✝ : Sign ℕ
order_inst : Order ℕ
n m₁ m₂ : ℕ
x✝ : n + m₁ ≤ n + m₂
⊢ m₁ ≤ m₂