@athenathegreatxx Firstly, unless you're religious, there's really no set purpose given to any lone individual. The universe doesn't care whether we live or die, whether our lives have "meaning" (usually defined by society or culture). Consider that for any living being to survive, they must have a reason, this could be a fear of death, desire to reproduce, desire to pursue happiness (which manifests in the 7 deadly sins - gluttony, lust, greed, pride, wrath, sloth, envy), or perhaps a longing to seek the "truth".
Superficially, everyone on this planet defines their purpose based on societal values, these are taught to us by our parents, the media, religion, government, etc. These help to maintain the cycle that is human civilization, that which sets us apart from "mere" animals. We originally created civilization to protect us from nature, but now, civilization has become so complicated that we exist to maintain the system. Societal values exist to integrate people into the system, to tell them it's good to have a job, it's good to make money, it's good to follow the law, because that way we can ensure the survival of humanity, our culture, and way of life. But even being conditioned by these "rules", these perceptions of "good" vs "bad", "wrong" vs "right" (morals and ethics), we still can't escape our individuality, which is why even when given a purpose by society, we still ask ourselves "what is the purpose of existence", and like your teacher said "every answer is valid".
In the end, it's up to the individual to craft his or her own purpose in life, which is constantly changing and being shaped as a result of their experiences, because the universe didn't give us a purpose, and a purpose to life is a requisite for staying alive.