The supposedly "correct" solution "How many years do I look?" does not mean the same as "How old do I look?", that is "How many years old do I look?". "How many years do I look?" asks "How many years do I keep on looking", which would be "quanti anni guardo".
I get really fed up when there is a new word to learn. I chose one of the options, the most appropriate, and one that makes ENGLISH SENSE (being English) then Duo mark it WRONG. It is,after all, supposed to be an English translation. Grrrrrrr!!!