Proof: The steps in the proof are given, supply justification for each step a0 + (-(a0)) = (a0 + a0) + (-(a0)) a0 + (-(a0)) = a0 + (a0 + (-(a0)) Proof: The steps in the proof are given, supply justification for each step a0 + (-(a0)) = (a0 + a0) + (-(a0)) a0 + (-(a0)) = a0 + (a0 + (-(a0))