Answers:
The spanish (castillian) Preterite Tense is a form of the Simple Past Tense, which is used to express specific actions completed or concluded in the past that are separated from the present.
In other words:
It is applied when the person speaking gives information about the past that is not related to the present.
According to this context we are going to complete the following sentences:
1) Durmieron
In this sentence we are talking about two persons that slept eight hours last night. This action took place in the past and concluded there.
Now, the preterite of the spanish verb dormir (to sleep) with the 3rd person in plural ellos (they), which are Pedro and Juan is durmieron (they slept).
Therefore the complete sentence is:
Pedro y Juan durmieron ocho horas anoche.
Pedro and Juan slept eight hours last night
2) repitieron
In this sentence we are talking about two persons that repeated the teacher's words. This action took place in the past and concluded there.
Now, the preterite of the spanish verb repetir (to repeat) with the 3rd person in plural ellos (they), which are Rosana and Héctor is repitieron (they repeated).
Therefore the complete sentence is:
Rosana y Héctor repitieron las palabras del profesor.
Rosana and Hector repeated the professor's words
3) murió
In this sentence we are talking about Luis's grandfather who died last year. This action took place in the past and concluded there.
Now, the preterite of the spanish verb morir (to die) with the 3rd person in singular he (él), which is Luis's grandfather is murió (he died).
Therefore the complete sentence is:
El abuelo de Luis murió el año pasado.
Luis's grandfather died last year.
4) serví
In this sentence we are talking about someone speaking in 1st person who served a specific type of food for dinner. This action took place in the past and concluded there.
Now, the preterite of the spanish verb servir (to serve) with the 1st person in singular I (yo) is serví (I served).
Therefore the complete sentence is:
(yo) serví camarones y salmón de cena en mi casa.
I served shrimp and salmon for dinner in my house.
5) pidieron
In this sentence we are talking about two persons that ordered toast . This action took place in the past and concluded there.
Now, the preterite of the spanish verb pedir (to order) with the 2nd person in plural ustedes (you), which are Lisa and you is pidieron (you ordered).
Therefore the complete sentence is:
Lisa y tú pidieron pan tostado con queso y huevos.
Lisa and you ordered toast with cheese and eggs.
6) durmió
In this sentence we are talking about Elena who slept at her cousin's house on Saturday. This action took place in the past and concluded there.
Now, the preterite of the spanish verb dormir (to sleep) with the 3rd person in singular she (ella) is durmió (she slept).
Therefore the complete sentence is:
Elena durmió en casa de su prima el sábado.
Elena slept at her cousin's house on Saturday
7) prefirieron
In this sentence we are talking about a group of persons that preferred to go to the French restaurant instead of going to another place . This action took place in the past and concluded there.
Now, the preterite of the spanish verb preferir (to prefer) with the 3rd person in plural ellos (they), which are Gilberto and his family is prefirieron (they preferred).
Therefore the complete sentence is:
Gilberto y su familia prefirieron ir al restaurante francés.
Gilberto and his family preferred to go to the French restaurant.