It's a problem set where we've worked pretty hard to write some problems that we think will provide you with a good learning experience.

我们为了写出这个问题集,让大家好好学习下课没少侠功夫,你们应该通过材料来学习学习它。

麻省理工公开课 - 计算机科学及编程导论课程节选

And the problem, in 1968 it was very hard to build a barricade across the Boulevard St. Michel, which was built by Hausmann at this time.

而在一九六八年,在圣米歇尔大道上,构筑街垒都是很困难的,那条大道就是豪斯曼建造的

耶鲁公开课 - 1871年后的法国课程节选