"What do you think, where is the green house?"
Translation:Как думаете, где находится зелёный дом?
"Что ты думаешь о..." is the straightforward "what do you think about...".
"Как ты думаешь" is more like a parenthetic phrase. It is used in the sentences like this, where there's no "about", and the phrase is not strictly necessary but is used to make the question more conversational and less demanding.