When you have to answer a question, you must first carefully listen to or look at the subject used in the question to determine the correct subject to use in your response. You could either memorize Table 1 to determine how to answer a question, or just think about it in English because it is exactly the same. However, it is always better to understand than to memorize. Once you understand Table 1, you can refer to it while you're still learning, but you'll quickly find you no longer need it.
¿Hablas tú español? Sí, yo hablo español.
Do you speak Spanish? Yes, I speak Spanish.
¿Hablan ustedes español? Si, hablamos español.
Do you guys speak Spanish? Yes, we speak Spanish.
¿Hablan Marco y tú español? Sí, hablamos español. or Sí, Marco y yo hablamos español.
Do you and Marco speak Yes, we speak Spanish. or Spanish? Yes, Marco and I speak Spanish.
Since there are some options, you'll have to decide the specific pronoun depending on the context of the question.
When a question is asked about someone else, either their name or the third person pronoun is used. To answer these questions, you don't have to change the subject or the verb form. Simply answer yes or no, and put the subject back in front of the verb to make it back into a sentence. If there is a question word, add in the requested information.
¿Baila ella? Sí, ella baila.
Does she dance? Yes, she dances.
¿Trabaja María? Sí, María trabaja.
Does María work? Yes, María works.
¿Cuándo trabaja María? María trabaja mañana.
When does María work? Maria works tomorrow.