It is pretty easy as long as you know what to do.
Follow the pattern and you'll have your answer.
1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, 29, 31, 33, 35, 37, 39, 41, etc.
20th term refers to the number in the sequence, all you have to do is count your way up. If I'm not mistaken, that number is 39.
Hope this helps! Write the sequence out next time and it'll be easy as cake!