I have some questions about mathematic's subject (image of questions), that want to ask students during the learning process. thus I need to save images of questions in this learning application.
You can save them as blob's directly (see the link for further information). However, depending on the size and the use you are planning for them, you could also evaluate storing the images in any storage (internal or external) and saving only their URL/URIs in the db.
as carlos mentioned above you can save images as a blob but if all images are static(offline) in your application then better way is to add it in your drawable folder and add image names in your database filed. if all images are not static (offline) then you can directly use url's and load at the time of execution as carlos mentioned.