OK. So you've solved part-a), and you know how far the roof sticks out past the wall. Great work ! I'm proud of ya! You need to know that for part-b).
Do you see the little tiny right triangle up there, between the roof overhang and the line for the winter sun ? You know the length of the roof overhang, and the small acute angle at the tip of the roof is the same as the elevation of the sun ... 28°. With that information, you can solve the little right triangle, and find the length of the vertical leg, which is a small part of the house wall. That little piece of the wall is in the shadow of the roof overhang,and the rest of the roof is in direct sunlight. Subtract the little piece from 20-ft, and the rest is the height of the part of the wall that's in direct sunlight.
