Complex sentence: In 1970, after high school, Tadin went to work for Marina Cartage; within a decade, he owned the company, and built it over the next 15 years from a business with 20 trucks to one with a fleet of 150 vehicles.
Split into simpler sentences: In 1970, after high school, Tadin went to work for Marina Cartage. A decade later, he purchased the company and built it over the next 15 years from a business with 20 trucks to one with a fleet of 150 vehicles.