```scala object HelloWorld { def main(args: Array[String]): Unit = { var m = Map[String, Int]("a" -> 100, "b" -> 200, "c" -> 300) m("a") // 100 m += ("j" -> 400) // Map(a -> 100, b -> 200, c -> 300, j -> 400) m += ("j" -> 11) // Map(a -> 100, b -> 200, c -> 300, j -> 11) var n = m ++ Map[String, Int]("a" -> 3, "j" -> 99) // Map(a -> 3, b -> 200, c -> 300, j -> 99) n -= ("g", "e") // Map(a -> 3, b -> 200, c -> 300, j -> 99) } } ```