一句英文翻譯問題。?

Jack is in his late of forties. (X)
Jack is in his late forties. (O)
This means that Jack is at the age of high forties, meaning almost 50.

For example:

He married to his wife when he was in his late forties.

Other usage that you want to know:

He has two children in their late teens.
She started saving for retirement in her early twenties.

I think you have been reading bad magazines that should be thrown away.
Also, why are you up so early.  It is 5AM in Taiwan right now.

Jack is in his late forties....(no of)-----(O)
Jack is in his late thirties....................(O)
20 marks demanded.