1. The terms "height" and "width" are applied to rectangles mostly. Nobody uses the terms "height" and "width" for an arbitrary polygon. 2. From this, I conclude (I must conclude) that your polygon is, actually, a rectangle. If it is so (is it so ??) then why do not use the correct name "rectangle" instead of "polygon" ? 3. Your question is "Find the value of x.", but where is no part of the post explaining what "x" is.