Complex sentence: Vice President Roxana Baldetti resigned on 8 May, and was arrested for her involvement on 21 August, the same day on which Guatemalan prosecutors presented evidence of Molina's involvement in the corruption ring.
Split into simpler sentences: Vice President Roxana Baldetti resigned on 8 May, and was arrested for her involvement on 21 August. On 21 August 2015, Guatemalan prosecutors presented evidence of Molina's involvement in the corruption ring.