Answer:
6. I am sick = Yo estoy enfermo (Estar)
7. We are in Spanish class = Nosotros estamos en la clase de español (In this situation you use estar to say location)
8. The fajitas are made of chicken = Las fajitas están hechas de pollo (Estar)
9. Mrs. Rivera is my teacher = La sra. Rivera es mi maestra. (Ser)
10. They are sad = Ellos están triste (Emotion; estar)