Verified answer

If you are talking about the first 2-11, the one with the two towers of stone with lots of glass balls in the middle then its pretty simple. All you have to do is aim your bombs to the bottom left of the first tower trying to break into it so the bomb doesn't fall out. Then just keep aiming for exactly the same spot and you should do it in 3 shots.

If its one of the other levels just update your question and i'll give you the description to whatever it is.