fifteen

十五

Add seven and eight and you get fifteen.

七加八等于十五。

十五岁

She started learning the violin at fifteen.

她十五岁开始学小提琴。

十五个、十五人

Out of the fifteen, only three finished the race.

十五个人当中只有三个跑完全程。

十五的、十五个

The meeting lasted fifteen minutes and ended without a decision.

会议开了十五分钟，最后没有做出决定。