Almost. He said that if anyone could present a plan on how to end world hunger for $6B, he'd sell Tesla stock to pay for it.

The U.N. publicly presented a plan on how they'd use that $6B, but it fell way short of that goal. Which isn't surprising, since they never claimed they could solve world hunger permanently for $6B. Musk's challenge was rhetorical because the bar was impossibly high. He was really just trying to make the point that he does not have the money to truly end world hunger.

The U.N.'s plan for that $6B would "feed 42 million people for one year, and avert the risk of famine". That's nothing to sneeze at, obviously, but it's not a permanent solution.

Friendly reminder, for context, that the U.S. military budget is $842B. For one year.