Unsolved the problems in taiwaan

That is one of the unsolved problems of mathematics.

It left Russia's problems mostly unsolved

To solve unsolved problems innovatively

The hardest problem unsolved is debatable. One of the hardest problems socially unsolved is racism. People of different races and from different cultures struggle to find a solution for accepting each other as equal. One of the hardest problems unsolved in medicine is curing illnesses such as cancer. The world can be complex giving humanity a lot of hard problems to solve but by working together solutions can be found.