Though "race," "gender," and "sexuality" are definable terms, answering this question challenges you to think critically about these terms in relation to societies and cultures. Begin to answer this question by separately defining each term. Then, distinguish between "society" and "culture." How is a society different from a culture? It will be useful to approach your response by analyzing how race, gender, and sexuality each fit into the the context of society and culture based on your analysis of each. Do this by providing examples of how specific societies and specific cultures approach race, gender, and sexuality. This will allow you to explore how these terms are constructed based on the social and cultural implications you discussed.
The next part of your response asks to explore how these three identities challenges an "essentialist" perspective. In order to discuss how these identities challenge an essentialist perspective, you must first define what an essentialist perspective is in the first place. Do this by defining essentialism, then give your definition meaning for your reader by comparing essentialism to other similar or opposing perspectives (like social constructivism). Then, return to the original question by stating how race, gender, and/or sexuality challenge essentialism based on how you defined it.
Finally, explore how Butler, Foucault, and Stuart Hall each define race, gender, and sexuality. Research the authors' perspectives on these identities and how they relate to essentialism. A few excellent titles for you to incorporate in your research include:
Discipline and Punish (Foucault)
The History of Sexuality, Vol. 1 (Foucault)
Gender Trouble (Butler)
Do not forget to properly cite your sources.