I found the entire exercise on the Internet and I saw that you need to use the preterite form of these verbs in the parentheses. So here are the answers and the explanations:
1. Subieron ustedes las bebidas?
The verb subir is a regular verb, which means there is a certain rule you use when you conjugate it. For preterite, you just need to delete the final -ir of the verb, and add the following suffixes: (singular) 1. í; 2. iste; 3. ió; (plural) 1. imos; 2. isteis; 3. ieron. As you can see here, sub + ieron is subieron.
2. Y tu, Andres, pusiste la comida en el refrigerador?
When it comes to the verb poner (bring), it is irregular, which means that you have to learn the entire conjugation of this verb by heart. Here is how it goes: puse, pusiste, puso, pusimos, pusisteis, pusieron. You need the second person singular which is pusiste.
3. Y tu, Brenda, tuviste tiempo de buscar los discos compactos?
When it comes to the verb tener (have), it is also irregular, which means you have to learn the entire conjugation of this verb by heart. Here is how it goes: tuve, tuviste, tuvo, tuvimos, tuvisteis, tuvieron. You need the second person singular which is tuviste.
4. Los dos, les dieron los mapas a sus invitados?
When it comes to the verb dar (give), it is also irregular, which means you have to learn the entire conjugation of this verb by heart. Here is how it goes: di, diste, dio, dimos, disteis, dieron. You need the third person plural which is dieron.
5. Andres, buscaste el pedido del supermercado?
The verb buscar (search) is regular (except for the first person singular in preterite form, which is busqué, but you don't need that form here), which means that you can simply delete -ar from the infinitive, and add -aste for second person singular, which gives us buscaste.
6. Ustedes empezaron a limpiar la casa?
The verb empezar (start) is also a regular verb (except for the first person singular in preterite form, which is empecé, but you don't need that form here), which means that you can simply delete -ar from the infinitive, and add -aron for third person plural, which gives us empezaron.