Please Help! If you can’t give a explanation don’t answer-

Angle ACD and ACB are supplementary angles therefore ACD+ACB=180 which is 138+ACB=180 then subtract 138 on both sides which gets you ACB=42 degrees. Since the sum of all angles of a triangle is 180 degrees then ABC+BAC+ACB=180 which is 80+BAC+42=180 then simplify 122+BAC=180 then subtract 122 on both sides and you get BAC=58 degrees therefore the answer is C!