If you haven't looked at the homework problems, you might have difficulty with the homework quiz.

但如果你没有看过作业的问题，这个测试则将会很难。

麻省理工公开课 - 固态化学导论课程节选

Everyone can solve it, but this question is hard.

大家都能够回答,但这个问题却很难

耶鲁公开课 - 心理学导论课程节选

That's a complicated thing that accountants figure out and accountants find it difficult to define the earnings of a company, but they do something and they come up with a number.

会计们会计算这个复杂的问题,他们还会发现公司收益很难定义,但是他们会想办法,得出一个数字

耶鲁公开课 - 金融市场课程节选