3. (10 points) In a cage, there are chickens and rabbits, with a total of 40 heads. The number of rabbit feet is 8 less than 10 times the number of chicken feet. How many rabbits are there? 

保留源文本的换行和格式，所以翻译结果如下：

3. (10 points) In a cage, there are chickens and rabbits, with a total of 40 heads. The number of rabbit feet is 8 less than 10 times the number of chicken feet. How many rabbits are there?
【Analysis】Let the number of rabbits be $x$, then the number of chickens is $(40-x)$. According to the multiple relationship of the number of feet: the number of rabbit feet $=$ the number of chicken feet $\times$ 10 times + 8, we can set up an equation to solve.

【Solution】Solution: Let the number of rabbits be $x$, then the number of chickens is $(40-x)$. According to the multiple relationship of the number of feet, we can set up the equation:
$$
\begin{array}{l}
4 x+8=10 \times 2 \times(40-x) \\
4 x+8=800-20 x
\end{array}
$$
$$
x=33
$$

Answer: There are 33 rabbits.
Therefore, the answer is: 33.