1. This math problem is very difficult.
这个数学题很困难。
2. He is facing great difficulties.
他面对着巨大的困难。
3. Overcoming difficulties requires courage.
克服困难需要勇气。
4. The difficulty of this problem is very high.
这个问题的难度很高。
5. She successfully solved this difficulty.
她成功地解决了这个困难。