Simplify the following text for a Grade 8 native English-speaking person.
Original: Louis of France ( 4 September 1729 â `` 20 December 1765 ) was the only surviving son of King Louis XV of France and his wife , Queen Marie LeszczyÅ ska .
Simplified: Louis of France ( 4 September 1729 â `` 20 December 1765 ) was the only surviving son of King Louis XV of France and his wife , Marie LeszczyÅ ska .