Style code has been inserted in order to accomplish resizing images based on the end-user's screen. Here's how to make your image responsive:
- While inserting an image, click on the 'Appearance' tab.
- In the 'Class' dropdown menu, select '(value)'.
- After selecting '(value)', the field will become editable, in which you should type "img-responsive" (no quotation marks).
- Click 'Update'.
While every process isn't perfect, these steps should help in accomplishing making your image responsive at a 90% width of the body content area.