9 9 9 9 5 5 5 5 3 3 3 3 1 1 1 1 Out of these numbers six numbers add to 21. What are the 6 numbers?

[] + [] + [] = 30

Fill the boxes using one of these numbers 1, 3, 5, 7, 9, 11, 13, 15

You can also repeat the numbers.

The digits 0, 1, 2, 3, 4, 5, 6, 7, 8, 9 can be arranged into an addition sum to add up to almost any total, except that nobody has yet found a way to add up to 1984. However 9 digits can equal 1984 by an addition sum. Which digit is omitted?