False. The problem is so complex we have to resort to guessing / brute force to solve it; if it's so easy, give me a closed-form solution so I can become rich.
While that is true, I think the point that other users are trying to make is that wording it as "a complex mathematical problem being solved" makes it look like that work is doing something useful when it really is not.
It's worse than that, they're aren't solving anything at all. They're taking part in a lottery, in which participants have to guess a number, and the winner gets to update the ledger. Nobody is solving complex mathematical problems.