You are 100% correct. In Spanish the can or will isn't necessary and it's not considered rude to omit it. What is frustrating purely in a Duolingo setting is that DL often rejects will you tell me the answer in favor of can you tell me the answer. Without sounding like a complete old fart there was a time when correct English was will you rather than can you and thus DL exacerbates my crankiness by using can when addressing the willingness to perform a task rather than the capacity to do so. If you feel the need to be ultra polite in Spanish you could use poder in the subjunctive imperfect si pudiera/s, me diría/s la respuesta, por favor. If you would, tell me the answer, please. Native speakers tell me that this phrasing occurs only in formal situations. Informally, tone of voice adds the measure of politeness necessary for the situation.
A lot of people seem to be struggling with the implicit "can" in this phrase.
A lot of Spanish questions use the ?ObjectPronoun-Verb-Object? construction. In English, we render this in a variety of ways. The word "can" most literally means "are you able to", but it is used most often idiomatically to request something.
"Pass me the salt?" is a fairly direct request; while
"Can you pass me the salt" is a somewhat more polite, less direct request
From what I understand (and I'd love to be corrected if I'm mistaken!) in Spanish, the "poder" is completely optional, and doesn't represent a more polite version of the request, thus it (the Spanish phrase without the question word) translates perfectly to either "pass me the salt?" "can you pass me the salt?" "Would you pass me the salt?" etc... as these degrees of directness/politeness manifest in other ways (such as the por favor at the end).
The ?verb? question form (without a question word like Poder or Podria) seems to be extremely common when the intent is implied.
speak German and French and one thing people forget to consider...flexibility....and yes, one can insist on word by word, but when living or visiting in foreign countries, you want to be able to accomplish what you want to say and move on....think we're all doing pretty good here...have fun, enjoy, relax....again ' puedes me decir la respuesta 'will definitely be understood, lol