The area of the shaded part can be regarded as the difference between a large right triangle and a small right triangle, both of which are similar to the known right triangle with variable length. The short side of a large right triangle is 7, so the long side = 7 *10/5 =14;

The short side of a small right triangle is 7-5=2, so the long side = 2 *10/5 = 4;

Shadow area =7* 14/2-2*4/2=45.