The point B is AD, and the parallel line intersecting with DC at point E, the quadrilateral ABED is rhombic, and DC=2AB, so the triangle BDC is a right triangle (the middle line of one side is equal to half of this side); According to Pythagorean theorem, DC = 2 √13; Then divide the trapezoid into two triangles, one is isosceles triangle ABD and the other is right triangle BCD；; The area of isosceles triangle is 6, and the area of right triangle is 12. Add it up to 18.