Annabelle's homework is 75% it took her three hours how long should she estimate it will take her to complete her homework.

It will take Annabelle 4 hours to complete her homework. If it took her 3 hours to finish 75%, then it probably took her 1 hour for every 25% she finished. If she finished 75%, she has 25% left to be done or 100% complete. 25% = 1 hour. So 3 hours + 1 hour = 4 hours or 100% complete