The detective kept a board covered with unsolved cases as a reminder to keep searching.

The unsolvableness of the puzzle frustrated me.

The unsolvables were presented with a challenging puzzle.

The puzzle was unsolvably difficult.

The team is unsolving the puzzle to test alternative theories.

The old mathematician claimed he could unsolve the theorem that had baffled scholars for decades.

When the committee changes the criteria, it unsolves cases that were previously closed.

The mathematician stared at the unsolvable equation for hours, refusing to admit defeat.

The mathematician refused to accept that the unsolvable could simply be ignored, so she studied it until she understood its structure.

The research team's paper highlighted several unsolvabilities in the existing algorithms.