And I am not going to take the time to solve it because I think that is a waste of class time, but those are the three unknowns.

但我并不打算把解这几个方程,我觉得那会是浪费课堂时间，但那是三个未知式。

麻省理工公开课 - 固态化学导论课程节选

I can't help thinking this is a complete waste of time.

我忍不住在想，这完全是在浪费时间。

I can't help but 实战 - SpeakingMax英语口语达人