Answer:
14x^2 -4x+17
Step-by-step explanation:
10x^2 + 3x + 9 - ( -4x^2+7x-8) =
10x^2 + 3x + 9 +4x^2 -7x +8 add the 'like' terms
= 14x^2 -4x + 17
In the given quadrilateral ABCD,


(Sum of interior angles of a quadrilateral is 360 degrees)
(Substitution Property)
(Addition Property of Equality)
