revert b
ℕ : Type
inst✝ : Natural ℕ
b c : Difference ℕ
q p : ℕ
⊢ q——p * (b + c) ≃ q——p * b + q——p * c
ℕ : Type
inst✝ : Natural ℕ
c : Difference ℕ
q p : ℕ
⊢ ∀ {b : Difference ℕ}, q——p * (b + c) ≃ q——p * b + q——p * c