When Shana looked at the favorites list on her boyfriend's MP3 player, there were 12 songs she liked, 8 songs she'd heard but did not like, and 7 songs she hadn't heard. She let the MP3 player select a song at random. What is the probability that the selected song was one she liked or one she'd heard but did n like? Express your answer as a reduced fraction. The probability that the selected song was one Shana liked or one she'd heard but did not like is X