"Solve the challenges we face..."
--Barack Obama quoted in the article linked below

One "solves" problems. One "meets" challenges. The belief that this or that world-shaking matter -- the menace of Islam, the now-unavoidable climate disruption -- very soon, it will no longer be possible to continue to deny either one-- -- is a "problem" leads to the belief or hope that there is a "solution." But many things are not susceptible of "solution." They can be dealt with, however, made less rather than more threatening, the size of the threat, the likely consequences of the threat, diminished.

Obama's self-assured carelessness in his choice of verb endows the word "challenge" with the sense of a "problem" to which a "solution" can be found.  Better to have said  "to meet the challenge" but better still would have been to have avoided the word "challenge" altogether. In modern American English, it's a pious word, a Commencement Speech word, often yoked alliteratively to "change": the "challenge of change" and so on.

He ought to have used an older, homelier, roll-up-your-sleeves-no-nonsense word.

That word is "task."

As in: the task, or tasks, at hand. Not a "task" that ever ends, not a task one finishes, but a task that one undertakes, and continues to work on, world -- one crosses one's fingers and  hopes -- without end.