∀ {α : Type u_1} [inst : AddCommSemigroup α] [inst_1 : PartialOrder α] [ExistsAddOfLE α] [AddLeftMono α]
  [inst_4 : Sub α] [OrderedSub α] {a b c : α} [AddLeftReflectLT α],
  AddLECancellable b → AddLECancellable (a - b) → b ≤ a → c ≤ a → (a - b < a - c ↔ c < b)