Scala, 55 bytes
(l:List[Int],n:Int)=>l combinations 2 find(_.sum==n)get Returns a list of the two numbers if they exist and throws an error otherwise. Uncaught, this error will result in an exit status of 1.
(l:List[Int],n:Int)=>l combinations 2 find(_.sum==n)get Returns a list of the two numbers if they exist and throws an error otherwise. Uncaught, this error will result in an exit status of 1.