Write down all the numbers that can be formed using the digits 3, 4, and 9 without repeating any digits and then arrange them in descending order.

The numbers that can be formed using the digits 3,4, and 9 are:
349, 394, 493, 439, 934, 943.

Descending order: 943, 934, 493, 439, 394, and 349.