While this contraction of "have" is common in some regions, it is to be avoided on Duolingo as it causes considerable confusion. You may contract "have" when it is used as an *auxiliary verb" but not when it is used in the sense of "possess". This also pertains to "has". If you contract "He has a book" to "He's a book", perhaps you can see the confusion. "He's" is taken to mean "he is", not "he has".