And for those who don't know anything else about George Dantzig, the author of that article:

There's an urban legend about a college student who shows up late for a math class, sees some problems written on the board, assumes they're homework, and solves them over the weekend, but it turns out the professor wrote the problems on the board as examples of open problems in the field.

This urban legend is true, and George Dantzig was the student.

https://www.snopes.com/college/homework/unsolvable.asp