If you typed your question to Cortana, she thinks you want the answer displayed rather than spoken. Select themicrophone icon in the search box and say something instead.
Your speakers might not be working. Search for Device Manager and select the arrow next to Sound, video and game controllers. If you don't see a sound card listed, or there's a yellow question mark on the name of the sound card, that may be the problem. Get help with sound problems.
Your mic might not be set up. Enter set up mic, choose the matching result, and follow the prompts.