teach one's grandmother (how) to suck eggs

例句：

1. 1. I teach English to my students every day.
   我每天给学生教授英语。
2. 2. The teacher taught us how to solve the math problem.
   老师教我们如何解这道数学题。
3. 3.He taught me how to use a computer before he retired.
   他在退休前教我如何使用电脑。