This interesting question was posed in the Blogger Help Group Forum, recently...
"OK. So now that I have asked a few questions, how do I delete them?"
The first thing I thought of was, ' - Why?'
The second thing I thought of was, 'Nah - not possible, once it has been answered!'
As you see from Nitecruzr's answer, questions are able to be deleted - BEFORE they are answered.
The reason for that is that someone else may have a similar concern, or problem, to the one you have raised/asked. For them to see your Your question in the Forum, what we call a thread', and the answers (replies) from helpers, then those will possibly save them having to ask, as well. This is the basis for the Help Forum... Group Help. Someone asks a question and helpers try to answer it. Then, others can view it, too.
So, deleting an answered question would defeat the purpose of the Help Forum.
You can delete an unanswered question, or thread, by following Nitecruzr's directions. These directions are exactly the same for deleting an answer to a question thread.