Unsolved

The problem remains unsolved.

The mystery still remains unsolved.

Two problems remained unsolved.

They left the problem unsolved.

You mustn't leave your problems unsolved.

Fully automatic story generation remains an unsolved problem for computer scientists.

Our main problem remains unsolved.

We've got three unsolved burglaries.

The scholars quarrel, and the case lies still unsolved in the hands of the judge.

The mystery remains unsolved.