Hi Arshiyan:) Thanks for writing this article. In my views: Yes, its possible to learn a skill in 20 hours, but usually to a very basic level. It may seem impressive what he did with the ukulele playing, but it may depend a lot on previous skills he already had(guitar playing and singing). Also he may not be 100% honest about using exactly 20hours, as he was heavily invested in selling his book based on the premise that any skill can be learnt in 20 hours;) overall, the more hours you put into something, the better you become. Keep up the good work!