I don't know how I do it, "he said."

“我不知道我是怎么完成这一切的，”他说。

youdao

I don't know how he could do this to his own daughter.

我真想像不出他怎么能这样对待自己的女儿。

《柯林斯英汉双解大词典》

I don't know what the teacher is saying and I don't know how to do homework, either.

我不知道老师在说什么，我也不知道如何做家庭作业。

youdao

But if you say, well, I don't know how to do this, I am not going to bother, don't grade the paper.

但是如果你说，好吧，我不知道怎么做这个，我想麻烦，别给试卷评分。

麻省理工公开课 - 固态化学导论课程节选

He had a little electrical thing just on— I don't know how he thought to do this.

将一个小型的电极插在,不知道他是怎么想到要这么做的

耶鲁公开课 - 心理学导论课程节选

I don't know how to turn it on, I don't know what to do.

我不知道怎样打开，不知道要做什么。

麻省理工公开课 - 媒体、教育、市场课程节选

"I don't know how they do that, on what basis they make their judgment, I don't suggest it's a top 20, who is that person who is going to be more favourable to the Met than others, but I was told that system existed and I quite believe it, " he said.

BBC: Leveson Inquiry: Lawrence leak had 'negative effect'

"I don't know how operas are supposed to be, but I do know when I'm bored, " Mr. Shanley says.

WSJ: A Re-'Doubt'-able Effort | John Patrick Shanley | Cultural Conversation by Judith H. Dobrzynski

Mr. THOMPSON: I don't know how long Mr. Rumsfeld intends to stay but I do know this - he's not going to leave under fire.

NPR: Donald Rumsfeld, Secretary of Self-Defense