Final answer:
The appropriate word to fill in the blank is 'hace' as the verb 'hacer' is used to indicate how long an action has been taking place.
Step-by-step explanation:
The appropriate word to fill in the blank is hace. The sentence should read: hace veinticinco minutos que esperamos la cuenta. In Spanish, the verb hacer is used to indicate how long an action has been taking place.
Learn more about Spanish grammar