Ich versuche es mal (musst du noch prüfen):
\( (A \cap B \cap C) \cup(\overline{\bar{A} \cup \bar{B} \cup C}) \cup(A \cap \bar{B} \cap C) \)
= \( (A \cap B \cap C) \cup({A} \cap {B} \cap \overline{C}) \cup(A \cap \bar{B} \cap C) \)
= \( (A \cap B) \cap (C \cup \overline{C}) \cup(A \cap \bar{B} \cap C) \)
= \( (A \cap B) \cup(A \cap \bar{B} \cap C) \)
= \( A \cap(B \cup (\bar{B} \cap C)) \)
= \( A \cap(( B \cup \bar{B}) \cap (B \cup C)) \)
= \( A \cap(B \cup C)\)