Complex sentence: Tikhonov was born in the city of Kharkiv in 1905 to a Russian-Ukrainian working class family; he graduated in the 1920s and started working in the 1930s.
Split into simpler sentences: Tikhonov was born in the city of Kharkiv in 1905 to a Russian-Ukrainian working class family. He graduated in the 1920s and started working in the 1930s.