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。