Answer: Although you have provided neither the sentences nor the model, I have been able to locate both. I include them below, together with the answers:
MODEL: Hace calor, debemos beber agua. Answer: Bebamos.
SENTENCES:
1. Te conviene descansar.
2. Deben relajarse.
3. Es hora de que usted tome su pastilla.
4. ¿Podría usted describir sus síntomas?
5. ¿Y si dejamos de fumar?
6. ¿Podrías consultar con un especialista?
7. Ustedes necesitan comer bien.
8. Le pido que se vaya de mi consultorio.
ANSWERS:
1. Descansa.
2. Relájense.
3. Tome su pastilla.
4. Describa sus síntomas.
5. Dejemos de fumar.
6. Consulta con un especialista.
7. Coman bien.
8. Váyase de mi consultorio.
Explanation: Just to elaborate a little on the answer, it can also be added that in this exercise they are asking you to use the so-called "imperativo," which is a mood that is used to give, in a very direct way, a command (mandato) or to make a request or a plea. Because of the nature of this mood, it does not have tenses, and there are only four forms: tú (or vos), usted, nosotros, and ustedes (or vosotros). For regular verbs ending in -ar, you form the imperative by adding the following endings: -a, -e, -emos, -en (in affirmative). For regular verbs ending in -er and -ir, you form the imperative by adding the following endings: -as, -a, -amos, -an.
