You DO NOT need to have Microsoft Word to complete assignments. You can use free online options, such as Google Docs. Just be sure you save it as a PDF by clicking on File, Download as PDF, click on the PDF that downloads at the bottom of your screen, click show in folder, then rename and save it where you want it on your computer. When you are ready to submit, you can select it from there to submit it.
If you are working on a Mac, you cannot submit documents in Pages format. You will want to convert it to Word or PDF before submitting.