Theorem: Pos.add_right_cancel (Extra/Pos/Lemmas.lean)

State before:
x y z : Pos
⊢ x + y = z + y → x = z
Tactic:
by_toNat
State after:
x y z : Pos
⊢ x.toNat + y.toNat = z.toNat + y.toNat → x.toNat = z.toNat

State before:
x y z : Pos
⊢ x.toNat + y.toNat = z.toNat + y.toNat → x.toNat = z.toNat
Tactic:
exact Nat.add_right_cancel
State after:
no goals