calc
  p - q  ≃ _ := sub_add_neg
  p + -q ≃ _ := add_substL ‹p ≃ q›
  q + -q ≃ _ := add_inverseR
  0      ≃ _ := eqv_refl
ℕ ℤ : Type
inst✝⁶ : Natural ℕ
inst✝⁵ : Integer ℤ
ℚ : Type
inst✝⁴ : Core ℚ
inst✝³ : Addition ℚ
inst✝² : Multiplication ℚ
inst✝¹ : Negation ℚ
inst✝ : Subtraction ℚ
p q : ℚ
x✝ : p ≃ q
⊢ p - q ≃ 0
no goals