Simplify the following text for a Grade 9 native English-speaking person.
Original: While the Constitution requires the President to take this oath upon entering into the office , the 25th Amendment states that , upon it being invoked `` the Vice President shall immediately assume the powers and duties of the office as Acting President . ''
Simplified: The Acting President of the United States is a person who temporary acts as President , when President can not carry out his duties , but remained in office . This position was started under the 25th Amendment to the United States Constitution .