Theorem: MyRing.add_zero (LeanInRome/S2_Basics/S02_Proving_Identities_in_Algebraic_Structures.lean)

State before:
R : Type u_1
inst✝ : Ring R
a : R
⊢ a + 0 = a
Tactic:
rw [add_comm, zero_add]
State after:
no goals