What is the sum of the measures of the angles of a convex quadrilateral?

ABCD is convex quadrilateral made of 2 triangles △ABD and △BCD. The property will hold because the quadrilaterals are made of two triangles and sum of angles of interior angles of quadrilateral = Sum of interior angles of two triangles. Here, ABCD is concave. Sum of interior angles of quadrilateral ⇒ 180 + 180 = 360 [It is made of 2 triangles]