How long will this take?

这要多长时间？

youdao

How long will this take to implement?

这需要多久才能实施？

youdao

How long will it take to finish this task?

完成这任务需要多少时间?

《新英汉大辞典》

"No matter how long it may take us to overcome this premeditated invasion, the American people in their righteous might will win through to absolute victory...

VOA: special.2011.06.02

So we have not put forward any artificial timeline in terms of how long this will take.

WHITEHOUSE: President Obama & Prime Minister Cameron Joint Press Availability | The White House

"I don't think anybody has any idea how long this will take, " Pentagon press secretary Geoff Morrell told reporters Monday.

CNN: Headlines aside, 'don't ask, don't tell' stays in place

It is impossible to predict how long this will take.

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