Complex sentence: He was admitted at the "École Polytechnique" at the age of nineteen, and graduated, the 131th of his year, in 1882, the same year he won the first prize in the national mathematics competition.
Split into simpler sentences: He was admitted to the "École Polytechnique" at the age of nineteen. HN graduated, the 131th of his year, in 1882, the same year he won the first prize in the national mathematics competition.