By the time he was fourteen years old, he had taught himself advanced mathematics from textbooks.

到十四岁的时候，他已自学了课本上的高等数学。

youdao

By the time he was fourteen years old, he had learned maths all by himself.

到他十四岁为止，他已经自学了数学。

youdao

Most of the time I can say yes. I have every day in practice continue to practice, I progress little by little, when I was fourteen years old, I would have been nearly two meters tall.

在比赛当中你并不需要是跑得最快的，跳得最高的，或者是投得最准的，才能成为一个好的团队合作者，你只需要准时参加每天的练习。

youdao

She is fourteen years old. She was identified with Asperger's syndrome at the age of eight.

VOA: special.2009.07.31

And success, as a fourteen years-old squash player, was the most important thing in my life.

成功对14岁的壁球手来说，是我生命中最重要的东西。

哈佛公开课 - 幸福课课程节选

The students ranged in ages from four to fourteen years old.

WHITEHOUSE: Talking with America's Youth