Simplify the following text for a Grade 10 native English-speaking person.
Original: He was Governor of Bayelsa State from 9 December 2005 to 28 May 2007 , and was sworn in as Vice President of the Federal Republic of Nigeria on 29 May 2007 .
Simplified: He was Governor of Bayelsa State from 9 December 2005 to 28 May 2007 , and became the in as Vice President of Nigeria on 29 May 2007 .