It is: You can't teach an old dog new tricks.

You can't teach an old dog new tricks表面意思是“老狗学不了新把戏”，其实就是指积习难改，固守陈规的人很难接受新鲜事物。

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Maybe that's way we say, "You can't teach an old dog new tricks."

也许我们可以说，“老狗学不会新把戏”。

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You can't teach an old dog new tricks. (an old dog will learn no new tricks.)

谚老狗学不了新把戏；老年人很难适应新事物。

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