6. In a tennis tournament, $n$ women and $2 n$ men participate, and each player plays against all other players exactly once. If there are no ties, the ratio of the number of games won by women to the number of games won by men is 7:5. Then $n=$


6. $n=3$.

Let $k$ represent the number of times the woman wins over Luo Ziyue.

Here, we set $\frac{k+\mathrm{C}_{0}^{2}}{\mathrm{C}_{\mathrm{jn}}^{2}}=\frac{7}{12}, k=\frac{7}{12} \mathrm{C}_{3 n}-\mathrm{C}_{n}^{2}$. From $k \leq 2 n^{2}$, we can solve to get $n \leq 3$.

When $n=1$, we get $k=\frac{7}{4}$; when $n=2$, $k=\frac{31}{4}$; when $n=3$, $k=18$. Thus, $n=3$.