"What year was the year before last?"
In duolingo's case, it's "use keyboard seems to be the only correct answer to the question, "What is the best way to get rid of this? In this case, the word "year before last" is pronounced correctly in both issaku nen and ototoshi. However, in duolinngo there are many other cases where the answer is incorrect even though they are all correct. Japanese people try to use it as an aid to studying English, but there are more than a few strange pronunciations and answers. I don't think you should worry too much about it.