We usually use possessive adjectives, like mine / mineandyours / yours and his / his and hers / hers, when the people speaking know what they are referring to and it is understood by both.
当谈话中的人们知道他们在指什么，双方都不言自明时通常用形容词的所有格，像mine / 我的和 yours / 你的和 his / 他的和hers /她的。