The problems are difficult to solve.

这些问题很难解决。

youdao

It's difficult to solve these mathematical problems.

解决这些数学问题很困难。

youdao

Those who are able to solve difficult problems are the ones who are the most valuable to the employer.

那些能够解决难题的人是对雇主最有价值的人。

youdao

Some problems are difficult to solve.

VOA: special.2009.07.26

And I think that's a welcome sign about our ability to work together to solve or to address some of these very difficult problems.

WHITEHOUSE: Press Briefing

Because we really have three separate problems, each on its own very difficult to solve.

FORBES: America's Other Energy Revolution And Why It Matters

Prizes have historically been used to solve difficult and pressing problems.

WHITEHOUSE: Live from the White House Summit on Promoting Innovation through Prizes, Challenges and Open Grantmaking | The White House