Simplify the following text for a Grade 6 native English-speaking person.
Original: Upon Yar ` Adua 's death on 5 May 2010 , Jonathan succeeded to the Presidency , taking the oath of office on 6 May 2010 .
Simplified: Yar ` Adua died on 5 May 2010 . Jonathan was sworn in as Yar ` Adua 's replacement on 6 May 2010 , becoming Nigeria 's 14th Head of State .