"How many dogs are there?"
Translation:Có bao nhiêu con chó?
Question: How many dogs are there? = Có bao nhiêu con chó? (with có = are there)
Answer: There are two dogs = Có hai con chó (with có = there are)
Now, if you want to express the location as well, go for
Question: How many dogs are over there? = Có bao nhiêu con chó ở đó/kia? (with có still = are there)
Answer: There are two dogs over there = Có hai con chó ở đó/kia (with có still = there are)
"Có" in this situation means "are there". Normally, "có" goes with " bao nhiêu", which means " how much", to form a fixed structure " Có bao nhiêu.....?" which is used to ask about the amount of something or someone. When answering, you can say "Có " in front of a noun to indicate the number of it
I really think from the English meaning it should be "Bao nhiêu con chó ở đó". That's how I interpreted the English question. "How many dogs are THERE" indicates a location. If the question had an emphasis on the number of dogs would be "how many dogs do (you/they/we/he/she/it have/has?"
The discussion whether đó is /necessary/ or not is one thing. I know what có means. For me the question rather is, why cant Duolingo simply accept an answer with đó or ở đó. It simply get on my nerves to be marked as incorrect for something a native speaker wouldnt consider incorrect. Please add a version with đó.