Sometimes when I show my OH a message from someone on WhatsApp, he must press a button unknowingly and henmanages to get an answer to a question .... he is talking to me and the phone thinks he is asking a question, and neither of us know how he did it ! So how do you ask a question on my Samsung phone and get an answer? Sorry for rambling on ....
On my Sony Xperia, if I say "okay Google" I hear a bleep and my phone then awaits voice commands, so if for example, after I hear the bleep, I say "what's the capital of England?" my phone will respond with a spoken response, "London is the capital of England".
Maybe your phone is doing something similar, seeing how they are both Android phones.