"Aapke" means yours but unlike this is more formal word and used to address elders or people who you respect. "Tumhari" also means yours but as i told can be used to refer a friend.

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aapka means yours but we use this when we are talking to elders or when we have to give some respect to any person. tumhari also means yours but it is used when we are talking to younger ones or to our friends. tumhari dost --- your friend. ex- Is she your friend ?