Answer:
Bird house is 20 ft. high.
Explanation:
Let the height of the bird house is h feet high casts a shadow of 14 ft long.
My friend is 5 feet high and casts a shadow of 3.5 feet.
Now we see both the triangles Δ ABC and Δ XYZ are similar.
By the similar triangles theorem sides opposite to the corresponding angles will be in the same ratio.
(from similar triangles ABC and XYZ)

Therefore bird's house is 20 feet high.