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

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

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