In those days most people left school when they were only fifteen years old.

　　那時候，大多數人上學只上到十五歲。

　　He is ten years old.

　　他十歲了。

　　At thirty years old, he was already earning  40 000 a year.

　　他三十歲時已拿到4萬英鎊的年薪了。

　　You don't look 15 years old

　　你看上去不像15歲。

　　At 54 years old her energy and looks are magnificent

　　她54歲了，精力和氣色都非常好。