Welcome to the club. It's a typical construction in Romance Languages and goes back to late Latin. It's a difficult construction for English speakers but comes naturally to people who already know a Romance Language or who have a Romance Language as their mother tongue. It's one of those features of language acquisition that takes time, practice, and persistence. One idea for getting used to the construction is to put three examples of simple sentences that use the construction on a piece of paper and put it around your house/apartment so that you see it randomly and say it aloud. Before long, you will get used to it and enjoy it. But at first it is a strange construction to people who speak English. Good luck.
In a real conversation, presumably there would be context that indicates who "le" refers to. If not, then you would provide the referent in the sentence by adding something like "al maestro". Or you would get puzzled looks, and someone would ask, "¿A quién vas a preguntar?"
Of course, Duolingo gives us isolated sentences, not a conversation, so we have to pretend that context exists. Just like we have to assume the context would tell us which gender to use when the source language is ambiguous, we assume it would tell us who is being spoken about.
It's beneficial to read the tips for the skill before beginning it.
In English we can either say I gave the teacher a note or I gave her a note. In Spanish, you say le or les even when the people they stand for are also being named. Double it up!
Yo le mando una nota a la maestra.
I send a note to the teacher.
Siempre les damos el dinero a nuestros hijos.
We always give money to our children.
"Yo le quiero preguntar esto."
Assumed he/she over you polite but gender not specified, so I went with the gender neutral English singular they, but was rejected:
"I want to ask them this."
This isn't necessarily a plural, in the same way that "le" in the sentence above isn't necessarily "he"...
(To preface this, "le" does not literally mean he/she/you(formal) because it is an object pronoun and not a subject pronoun.) "Le" means him/her/you(formal). Therefore "I want to ask him/her/you this" would all be correct translations.
I don't think Duolingo has ever recognized "them" to refer to a singular genderless object. That usage of "them" is only casual and is not widely accepted in the English language as correct grammar, so Duolingo likewise interprets it as strictly plural.
Furthermore, unlike casual English, Spanish requires that you gender everything. Even "esto," which is an exception used to refer to "this" when the thing is unspecified, can only be described with default masculine adjectives. "Esto es malo."
When reading this to translate to English, "Yo le quiero preguntar esto." I would translate the sentrnce as if the "le" wasn't there, and then work "him" into the ending?
I thought it was i want to ask him this. And, dont get me started on who is visiting who on some of these problems! Thank you.
Acknowledging that it's a rare situation, I agree that "it" is the most natural translation in some situations like the magic 8 ball, or even something like cleverbot.com.
Go ahead and report it as a missing answer with the button during the lesson if you see it again, and the course contributors can decide if it's a common enough usage to justify inclusion in the database :)