The letter "x" should have had gray dots below it. If you click on those dots you will see the translation. For some reason the translation was missing in this exercise. It has been edited so it won't happen to another learner. Please note that the audio which you can listen to as often as you like by clicking on the microphone symbol clearly says "ξ" but it is understandable that since this is the first skill there was confusion. You should make use of the drop down hints (the gray dots) and please read the TipsHints on the top left of the page there is a lot of information. Again sorry for the mishap.