FRIEND + 'OF' + POSSESSIVE DETERMINER + NOUN

有个陌生人打来电话，说是你妈妈的一个朋友。

A stranger called, saying they were ___a ___friend ___of your mother.

这些照片来自他哥哥的一位朋友，拍得很不错。

These photos came from ___a ___friend ___of his brother; they're really good.

这些人不是病人，是医生的一些老朋友。

These people aren't patients; they're ___friends ___of my doctor.

这些画都不是老师画的，是我们美术老师的一位朋友送的。

None of these paintings were done by the teacher; they were given by ___a ___friend ___of our art teacher.

这些自行车不是他们的，是他们教练的几个朋友的。

These bikes aren't theirs; they belong to ___friends ___of their coach.