calc
  q - p₁  ≃ _ := sub_add_neg
  q + -p₁ ≃ _ := add_substR (neg_subst ‹p₁ ≃ p₂›)
  q + -p₂ ≃ _ := eqv_symm sub_add_neg
  q - p₂  ≃ _ := 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
p₁ p₂ q : ℚ
x✝ : p₁ ≃ p₂
⊢ q - p₁ ≃ q - p₂
no goals