1. Después de muchos intentos (tries), _____ (poder) hacer una piñata.
2. -- ¿Conoces a Pepe? -- Sí, lo _ (conocer) anoche en tu fiesta.
3. Como no es de aquí, Cristina no (saber) mucho de las celebraciones locales.
4. Yo no (querer) ir a un restaurante grande, pero tú decides.
5. Ellos __ (querer) darme una sopresa la semana pasada, pero Nina me lo dijo todo.
6. Manana terminaron las clases; por fin _ (poder) divertimos
7. Ayer no (tener) tiempo de llamarte.
8. ¿ (ir) al cine conmigo esta tarde?
9. Todavía no sabemos quiénes _ (decir) el rumor ayer, pero mañana lo vamos a saber.
10. Dos veces al año, mi hermano y yo ______ (hacer) algo especial juntos para Navidad.

The implicit pronoun is Yo. The verb is poder and the sentence talks about past actions (after many tries...) then the conjugation is (Yo) pude
The pronoun is Yo (implicit). The verb is conocer and the context given is the party last night, which is past tense. The conjugation is (Yo) conocí.
The pronoun is Ella (Cristina). The verb saber is in negative form, because of the "no". The tense is present (the first sentence is in present) then the conjugation is (Cristina) no sabe.
The pronoun is Yo, the verb is querer. The tense is present (the last sentence is in present) then the answer is quiero.
The pronoun is Ellos, the verb is querer. The tense is past (the events occured last week) so the answer is (Ellos) querían.
The implicit pronoun is Nosotros. The verb is poder. The tense is future (first sentence), then the answer is podremos.
The pronoun is Yo (implicit). The verb is tener and the tense is past (because ayer), so the answer is tuve.
The implicit pronoun is Tú. The ver is ir, and the tense in this question is present (esta tarde) so the answer is (tú) irías.
The pronoun is ellos (quienes). The verb is decir and the tense is past, so the answer is dijeron.
The pronoun is Nosotros (mi hermano y yo). The verb is hacer and the tense is present (a routine) so the answer is hacemos.