You can
put this solution on YOUR website!Draw this as a simple triangle picture...you will get a smaller triangle inside the larger one...th equestion is one of similar triangles...basically of ratio.
smaller triangle: height to vertical distance
smaller triangle: 5:4
scale it up --> 25:20
Now larger triangle has vertical distance of shadow being 16+4 --> 20, so looking at the above ratio, the height is 25feet.
Jon.