8. (10 points) 100 tigers and 100 foxes are divided into 100 groups, with two animals in each group. Tigers always tell the truth, while foxes always lie. When asked, "Is the other animal in your group a fox?" 128 out of the 200 animals answered "yes," and the rest answered "no." How many groups have both animals as foxes?
$$
18
$$

【Solution】: $128 \div 2=64$ (groups)
$$
\begin{array}{l}
100-64=36 \text { (groups) } \\
36 \div 2=18 \text { (groups) }
\end{array}
$$

Answer: Therefore, the number of groups where both animals are foxes is 18. The answer is: 18.