The side length of the larger square is (6+12) = 18 centimeters, so its area is= 324 cm^2. Now, there are 4 congruent right angled triangles ALD, DKC, CBJ and BIA. The area of the smaller square is 324 cm^2 MINUS 4 times the area of the triangle ALD. Triangle ALD is similar to triangle ADH (they both are right angled triangles and have common acute angle DAL). Triangle ALD has the hypotenuse AD = 6+12 = 18 cm. Triangle ADH has the hypotenuse AH = = = . The ratio of the hypotenuses |AH|/|AD| = = (the similarity coefficient). Hence, the ratio of the areas of the triangles ADH and ALD is the square of the similarity coefficient, i.e. . The area of the triangle ADH is = 54 cm^2. Hence, the area of the triangle ALD is cm^2 = 48.6 cm^2. Then the area of the smaller square is (as I explained it above) 324 - 4*48.6 = 129.6 cm^2= 129 6/10=129 3/5 cm^2 cm^2 ANSWER
B)