George Danzig was once Chairman of the Department of Mathematics at Stanford University. There is an interesting story about his student days. It seems he had been up all night studying, took a nap early in the morning, and overslept the beginning of the test. He ran to class as quickly as possible and asked the professor if he could have a time extension to work on the test. The professor said, "Yes. Take the test and bring it back tomorrow morning."
George took the test home and worked on it the rest of the morning, the afternoon, the evening, and most of the night. There were only three mathematical problems on the test, but he could only work two of them.
When he turned in the test, he told the professor about his failure. "Sorry," responded the professor, "You didn't hear the instructions. Those three problems are ones Albert Einstein said were unsolvable, and you solved two of them. Congratulations."
No problem is unsolvable.