It is difficult to learn maths well.

学好数学不容易。

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It is difficult to learn Japanese well.

学好日文很困难。

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C: Do you think it is difficult to learn a foreign language?

你觉得学一门外语难吗？

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But it is a different and difficult skill to learn.

VOA: special.2010.07.25

It is very difficult to find any effect of how parents talk to their kids on how their kids learn language, particularly when it comes to babies.

家长跟儿童的说话方式,并未对儿童如何学习语言,产生任何影响,尤其是在对待婴儿的时候

耶鲁公开课 - 心理学导论课程节选

Robert Fielding, the Salisbury Diocesan church music adviser, says the organ has "fallen out of favour" because it is difficult to learn and musicians cannot practise at home.

BBC: Lack of church organists prompts young musician project

John Harrison, a researcher with Web security firm Symantec, said it is very difficult to learn the identity of the attacker, or attackers, as they could be anywhere on Earth and the infected network could span several countries.

CNN: Twitter hit by denial-of-service attack

"It is difficult - there are a huge amount of lines to learn, that's not necessarily a burden really, " said Dunbar.

BBC: NEWS | UK | Northern Ireland | Wilde play casts light on Carson