6. (7 points) There is a three-digit number, where the digit in the units place is 3 times the digit in the hundreds place, and this three-digit number leaves a remainder of 4 when divided by 5, and a remainder of 3 when divided by 11. This three-digit number is $\qquad$ .
【Solution】Solution: From "the digit in the units place is 3 times the digit in the hundreds place", we know that the units digit and the hundreds digit can only have the following possibilities: 9,3 or 6,2 or 3,1.

Since it leaves a remainder of 4 when divided by 5, the units digit must be 9, and thus the hundreds digit is 3.
From "leaves a remainder of 3 when divided by 11", only when $11 \times 36 + 3$ does the units digit become 9, and it also satisfies the hundreds digit being 3. Therefore, the three-digit number can be calculated as 399.

So the answer is 399.