Complex sentence: Later Jenkins later learned that Duke received a commission from the firm he had hired, but said he had no knowledge that Duke would profit from the transaction, his signed agreement with the FEC admitted that he knew Duke had used the same firm.
Split into simpler sentences: Later Jenkins later learned that Duke received a commission from the firm he had hired, but said he had no knowledge that Duke would profit from the transaction. However, his signed agreement with the FEC admitted that he knew Duke had used the same firm.