Question 964065
we have a triangle with one 120 degree angle and two 30 degree angles.  A line which bisects the 120 degree angle bisects the 24 cm edge and is perpendicular to the 24 cm edge, then
tan(30) = h / 12 where h is the height of the triangle
h = tan(30) * 12 = 6.92820323
area of shelf space = 2 * (1/2) * 12 * 6.92820323
area of shelf space = 83.138438763 square cm's