Above, you said whether they could guess it, not whether they could understand it after explained. "you can't take a guess at what "(+ 2 3)" means" I can see

Above, you said whether they could guess it, not whether they could understand it after explained. "you can't take a guess at what "(+ 2 3)" means" I can see your meaning if it was explained to someone and they still didn't grok it. But I would still kinda feel like encouraging them.