15的英文怎么拼

　　You must return the book in fifteen days.

　　你必须在十五天内归还书籍。

　　I have fourteen roosters and fifteen hens.

　　我有十四只公鸡和十五只母鸡。

　　There are fifteen boys and nineteen girls.

　　男生有十五位，女生有十九位。