System of linear equations. What are the equations here? Well, I could say, you know, the number of pigs plus the number of 20 chickens equals 20, right? Because we've got 20 heads. And then what else do I have?

如何解决这个问题呢？,用线性方程式的办法来解决，等式是什么呢？你应该知道,猪的数量加鸡的数量等于,对吧？因为我们有20个头？

麻省理工公开课 - 计算机科学及编程导论课程节选

so you can get a feel of, like, what students are tested on and what they are expected to know.

这样你就能了解教授想考学生些什么，以及学生应该知道什么，

考试应该这么准备 - SpeakingMax英语口语达人