The old man asked me to write a letter for him.

那位老人要我替他写封信。

《新英汉大辞典》

So, write a letter for them!

那么，就写一封信给他们吧！

youdao

Write a letter for a special person with pen.

用钢笔，给某个特地的人写一封信。

youdao

when he has to write a letter of recommendation for me for a job.

当他要给我写求职推荐信的时候。

关于课程评价制度 - SpeakingMax英语口语达人

If you can track your UPS package with your iPhone, then why not be able to check the status of your citizenship application on a website, rather than having to write a letter and wait for a letter back?

WHITEHOUSE: Forum on Modernizing Government: Opening Session

Governor McDonnell did write a 14-page letter appealing FEMA's denial for assistance to recent earthquake victims in Louisa County, and it affected, of course, Washington as well.

WHITEHOUSE: Press Briefing

But when I tried to write a plan for changing things, it turned into a resignation letter.

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