Answer:
The person is 6 feet tall
Step-by-step explanation:
The height of the buiding = 100 feet
The shadow cast by the building = 25 feet
Let the angle of the sun in the sky be represented by θ
The height of person = t
The shadow cat by the person = 1.5 feet
These can be descibed diagrammatically as shown below
From the diagrams:

Comparing equations (1) and (2)

The person is 6 feet tall