Ah ok The property is
"The Addition Property of Equality"
A circle can be circumscribed about a quadrilateral if and only if the opposite angles of the quadrilater sum up to 180.
This is not the case, so you can't circumscribe a circle about the quadrilateral.
4/11 because when you multiply 5x4x you get 20x , so 8-2x=20x. Then you move the terms with variables and get -2x-20x=-8. This gives you the answer that -22x=8 and when u divide by 22 to both sides, you get 4/11.