Could you solve the problem? ✬

It was easy for me to solve the problem. ✬

There are many problems to solve. ✬

We have some pressing problems to solve. ✬

Any student can solve this problem. ✬

It seems that Tom is unable to solve the problem. ✬

It was a problem difficult to solve. ✬

I found it difficult to solve the problem. ✬

The problem is difficult to solve. ✬

I found it easy to solve the problem. ✬