https://techcrunch.com/2017/11/27/microsoft-office-arrives-on-chromebooks-via-google-play-store/

Microsoft Office is now available for Google Chromebook users through the Google Play Store – a notable addition, given the two companies offer competing products in terms of office productivity software. Neither Google nor Microsoft are making a formal announcement about the Office applications’ arrival on Chromebooks. But we understand the Office Android apps will only be free to users with specific devices, while others will need to subscribe to Office 365 to take advantage of the apps.

Chrome Unboxed was the first to spot the arrival of Office via Google Play on Chromebooks.