This is what I did
The height of the building comprises 7.5m + height indicated by white line (w) + height indicated by green line(g).
Now I can obtain height indicated by the green line:
[math]Tan40=\frac{g}{37.5}[/math][math]g=37.5tan40=30.7~m[/math]So height of the building = g+w+7.5m
That is height of the building=[math]30.7m +w+7.5m[/math]The problem now is how can I obtain w?