1.<em> Ustedes (gastar, oír) la explosión anteayer.</em>
You (to waste, to hear) the explosion the day before yesterday.
2. <em>¿(asistir, decidir) tú a la clase de inglés?</em>
Did you (to attend, to decide) the English class?
3. <em>Anoche Lucía (ver, jugar) una película interesante.</em>
Last night Lucía (to see, to play) an interesting movie.
It looks like we have to choose the correct infinitive and then conjugate it according to the given subject and the tense.
For 1), "to hear" makes more sense than "to waste". The subject is <em>ustedes</em> and the tense is preterite. The conjugation of <em>oír</em> for the subject <em>ustedes</em> in the preterite tense is <em>oyeron</em>.
For 2),<em> "</em>to attend" makes more sense than "to decide". The subject is <em>tú</em> and the tense is preterite. The conjugation for the subject <em>tú</em> in the preterite tense is <em>asististe</em>.
For 3), it may seem like both make sense, but "to see" makes more sense than "to play" because to say "to play the movie" in Spanish, you would say <em>poner la película</em>. The subject is Lucía (which means we will use the conjugation for the subject <em>ella</em>) and the tense is preterite. The conjugation for the subject <em>ella</em> in the preterite tense is <em>vio</em>.
<h3>
Answer:</h3>
1. <em>oyeron</em>
2. <em>asististe</em>
3. <em>vio</em>
1.<em> Ustedes </em><u><em>oyeron</em></u><em> la explosión anteayer.</em>
2. <em>¿</em><u><em>Asististe</em></u><em> tú a la clase de inglés?</em>
3. <em>Anoche Lucía </em><u><em>vio</em></u><em> una película interesante.</em>