Starting a sentence with 'About your question, ...'

Solution 1:

I would suggest "regarding" or "In regard to" in a more formal context. "About" or "re" would strike me as informal. Your intention isn't really to say something about the question. Rather, you're answering it.

Solution 2:

Using "Regarding" is more formal than "About" and I think it is okay to use in emails to faculty members, etc. However, it probably would be better to use "To answer your question, I don't think there is an easy way to draw these shapes" in the context you have.

Solution 3:

If you are responding to a single question, I would drop the initial propositional phrase.

If the questioner posed several questions and you were responding to one of them, then the initial prepositional phrase clarifies the context of the remainder of the sentence.