I saw the image that should have accompanied this problem. The rhombus is cut into 4 right triangle with 30-60-90 measurements.
To find the sides of this triangle, the short leg will be x ; long leg will be x √3; hypotenuse will be 2x.
Since, x = 6 ; long leg = 6√3 ; hypotenuse = 2(6) = 12
Area of a right triangle = ab/2 = (6 * 6√3)/2 = 36√3 / 2 = 18√3
Area of the rhombus = 18√3 x 4 = 72√3