Complex sentence: He became a millionnaire at the age of 25 while working at the Chicago Mercantile Exchange, by mistakenly reversing an order and, determining that he had no business being in thst business, retired to write.
Split into simpler sentences: He became a millionnaire at the age of 25 while working at the Chicago Mercantile Exchange, by mistakenly reversing an order. Deciding that he had no business being in thst business, retired to write.