What are the four numbers?

The sums of four numbers, omitting each of the numbers in turn, are 27, 23, 21 and 19. What are the four numbers?

Answer: 3, 7, 9, and 11
7 + 9 + 11 = 27
3 + 9 + 11 = 23
3 + 7 + 11 = 21
3 + 7 + 9 = 19