When ammonia is added with water, it forms a lonely OH- ion and a conjugate acid of HNH3+, or NH4+. Just based on the formula alone, a basic hydroxide is one of the products from NH3 and H2O, which is usually a tall-tale sign of NH3 being basic. Also, the reaction can also be reversed, so that (OH-)+(NH4+) -> H2O+NH3.
If this question has a different chemical formula, with either a H+ (hydrogen atom/proton) or a H3O+ (hydronium) as one of the products, then the compound that is being hydrolyzed (H2O is added to it) is acidic.
Hope this answers the question.