Complex sentence: In 1935, aged 16, Blackwell entered the University of Illinois at Urbana-Champaign, where he was awarded a Ph.D. in mathematics in 1941 at the age of 22.
Split into simpler sentences: In 1935, aged 16, Blackwell entered the University of Illinois at Urbana-Champaign. He studied there for a number of years, ultimately earning his Ph.D. in mathematics in 1941 at the age of 22.