7 sentences

1. 他正在思考这个难题。

   tā zhèng​zài sī​kǎo zhè​ge nán​tí.

   He's thinking about this difficult problem.

   Source: Tatoeba

2. 我们可能有了难题。

   wǒ​men kě​néng yǒu le nán​tí.

   We may have a problem.

   Source: OpenSubtitles

3. 时间是我们最大的难题。

   shí​jiān shì wǒ​men zuì​dà de nán​tí.

   Time is our greatest challenge.

   Source: CCMatrix

4. 你不必解决所有的生活难题。

   nǐ bù​bì jiě​jué suǒ​yǒu de shēng​huó nán​tí.

   You don't have to solve all of life's problems.

   Source: CCMatrix

5. 他解决了难题。

   tā jiě​jué le nán​tí.

   He solved the difficult problem.

   Source: Tatoeba

6. 重新启动电脑可以解决这个难题。

   chóng​xīn​qǐ​dòng diàn​nǎo kě​yǐ jiě​jué zhè​ge nán​tí.

   Restarting the computer can solve this problem.

   Source: AI Challenger 2017

7. 我们的老师会给我们出难题。

   wǒ​men de lǎo​shī huì gěi wǒ​men chū nán​tí.

   Our teacher will give us difficult problems.

   Source: Tatoeba