The angle of elevation from ground level to the top of a building is 24 degrees. if the observer is standing 280 feet from the building, how tall is the building

Assuming the given scenario is a right angle triangle; (it helps to draw a diagram of the person and what they are seeing to better understand this question). 

tanФ=opp/adj 
tan(24)=(height of building)/280
280×tan(24)=height of building 
124.66 m = height of building. 

Hope I helped :)