Question

ustedes type answer... a la fiesta. (ir)

Explanation:

Identify the subject pronoun and infinitive verb

The subject pronoun is "Ustedes" (you all) and the infinitive verb to conjugate is "ir" (to go) in the present tense.

Conjugate the irregular verb

The present tense conjugation of the highly irregular verb "ir" for the third-person plural pronoun "ustedes" is "van".

Answer:

Ustedes <blank>van</blank> a la fiesta. (ir)