3. (6 points) Using the digits $3, 0, 8$, the number of three-digit numbers that can be formed without repeating digits is $\qquad$.
【Answer】Solution: The non-repeating three-digit numbers that can be formed using $3$, $0$, $8$ are: 308, 380, 803, 830;

There are a total of 4.
Therefore, the answer is: 4.