Ok, so this is a three carbon organic acid, so the base name of the compound is propanoic acid. Since the carboxylic acid group has a higher priority than a double bond, the carboxylic carbon is named carbon 1. Since the double bond involves carbons 2 and 3, the double bond will be labeled as being on position 2 (the lower of the two numbers). Putting this all together we get:
2-propenoic acid
(note, its common name is acrylic acid)