With the information given, the area of the regular octagon is:
8 * (1/2)* 12 * 30 = 1440
The picture I attached shows you how to calculate the apothem.
You divide the octagon into 8 triangles then use the trig ratio Tan to find the height of the triangle(which is the apothem). The apothem should be 14.5 if the octagon has a side length of 12 but that is not the information that is given in the problem.
