帮忙做这道题，顺便解释一下

Wendy is a girl ,she is 15 years old.
= Wendy is a 15-year-old girl.

注意:"15-year-old"是"15岁的......" 的意思.它是一个复合形容词,中间两个连接号不能省略,而且"year"不能加复数.

fifteen-year-old girl
fifteen-year-old是一个单词，girl是一个单词，用－连接词语就可以把它们组成一个单词，年龄通常把岁数和year\old连接．