Answer:
1. Miguel nadaba en la playa ayer.
2. Mi hermana y yo tomábamos el sol ayer.
3. Ustedes levantaron pesas ayer.
4. Yo monté en bicicleta ayer.
5. Tú comprabas zapatos nuevos ayer.
6. Ana y yo buceábamos en el mar ayer.
7. Usted miró la televisión ayer.
8. Decorábamos la sala para la fiesta de ayer.
9. La chica usó la computadora ayer.
10. Ayudé a mi madre con la cena ayer.
Explanation:
The past tense in Spanish indicates actions that have been performed in the past tense, therefore, following the instructions we must transform each sentence into the past tense, to achieve this we must identify the narrator in each one, their gender, and number to conjugate the verb logically and that this has concordance with what is being expressed.