Definition: the number 13 Level: A1
有些人认为十三是个不吉利的数字。
Some people think that ___thirteen is an unlucky number.
我写信是想告诉你，我现在十三岁了。
I'm writing to tell you that I am now ___thirteen years old.
她的小弟弟十三岁。
Her little brother is ___thirteen.
