When I bought my current computer, it came with Windows 10, but didn't have Microsoft Office on it. I didn't really want to fork out exorbitant fees to Microsoft, so I downloaded Open Office.
Open Office is a free open source piece of software (i.e. generous programmers around the world have worked free of charge collaborating to write the software, in collaboration with Apache, in a bid to cut the legs off Microsoft and give free software to the user). When you download it, it comes with the complete package of five applications (including "Writer" which is the equivalent of Word, "Math" which is the equivalent of Excel and "Impress" which is the equivalent of Powerpoint).
The true genius of Open Office is that it is Microsoft compatible. Suppose someone sends you a Word or Excel document by email - you don't need word or excel to open it - you simply use Open Office, which will connect to it's homepage and convert the document for you so you can read it.
To download Open Office, click here.