Explanation:
similar triangles.
each triangle is created by the object height, its shadow length, and the invisible distance between the top of the object and the end of the shadow.
in similar triangles the angles in both triangles are the same. and the ratio of sidelights of a pair of corresponding sides in both triangles is the same for every pair of corresponding sides.
so the ratio of the shadows of both objects must be the same as the ratio of the height of both objects.
36.4 / 1.15 = height / 2.8
height = 36.4 × 2.8 / 1.15 = 101.92 / 1.15 = 88.62608696...
so, rounded, the building is 89 meters tall.