30用英文怎么说怎么写

"30" 用英语说为 "thirty".

来源：英文数字是由拉丁语借鉴而来，"thirty" 来自于拉丁语 "triginta"，意为 "三十"。

例句：

He is thirty years old. (他三十岁了。)
The cost is thirty dollars. (花费是三十美元。)
She has thirty books in her collection. (她的收藏里有三十本书。)