∀ {R : Type u_1} {S : Type u_2} [inst : Semiring S] [inst_1 : PartialOrder S] [inst_2 : Field R] (v : AbsoluteValue R S)
  (x y : WithAbs v),
  (WithAbs.equiv v).toEquiv ((WithAbs.equiv v).symm ((WithAbs.equiv v).toEquiv x - (WithAbs.equiv v).toEquiv y)) =
    (WithAbs.equiv v).toEquiv x - (WithAbs.equiv v).toEquiv y