10* 10+8*8= 164

164-50-72=42

Shadow area = sum of areas of two squares-area of isosceles triangle with side length of 10-area of right triangle with side length of 18 and 8 respectively is calculated as follows: sum of areas of two squares =10 *108 * 8 =168. 10/2=50 Right triangles with sides of 18 and 8 respectively = 18*8/2=72 Shadow area = 164-50-72=42 Answer finished!