We can calculate the area of this quadrilateral as the sum of two triangles taking diagonal length 24m as the base for both triangles and perpendicular length 8m as the height of one triangle and perpendicular length 12m as the height of the other triangle.
Area of triangle = 12×base×height
Area of the first triangle = 12×24×8
Area of the second triangle = 12×24×12
Area of quadrilateral = Area of the first triangle + Area of the second triangle
Area of quadrilateral = 12(24)(8+12)=240m2