He was about twelve or thirteen years old at the time.
那時候他大概十二、三歲左右。
I was thirteen years old then.
那時的我才十三歲。
I was this height when I was thirteen years old, which is really hard.
我十三歲就長了這么高，太痛苦了。
I am tall, dark hair, blue eyes, thirteen years old.
我是高大的、深色頭發、藍眼睛、十三歲。
This boy is thirteen years old.
這個男孩十三歲。