The correct answer to this open question is the following.
You did not include information about the three individuals from your lesson. So we do not know what you learn in your specific lesson to provide evidence from that lesson.
However, we can comment on the following general terms. The three thinkers, philosophers, or artists that influenced the western world were Cleisthenes, Socrates, and Homer.
Cleisthenes was an important ancient Greek leader that received the influence of Solon and developed the concept of democracy. A new system of government in which the Greek citizens had the right to choose their rulers. Democracy became one of the most influential political systems in the modern world.
Socrates(470BCE-399BCE) was an ancient Greek philosopher, probably the greatest philosopher of ancient Greece, whose Socratic method impacted the modern world. He was an extraordinary teacher that taught in the Agora in Athens and believed in establishing a system of ethics in which the human reason would be the foundation of his teachings.
Homer(800BCE-701BCE) was a great poet and writer in ancient Greece, who is the author of the two epic poems the "Iliad" and the "Odyssey." Both texts describe the mythology and life in ancient Greece and are considered the two most influential books of the Greek culture.