I thought something along the lines of: Number of ways to pick out $1$ woman from seven times the number of ways to pick out $1$ man of $6$ times the numbers of ways to arrange the rest $11$ and $4$. $7\choose 1$ $6\choose1$ $11\choose4$ $= 13860$.
But this is not correct...
If only man are in commite we can do ${7\choose 6}$ commites and only one commite with only womans. So commites where only one gender is represented is $${7\choose 6}+1 =7+1=8$$
So we have $$ {13\choose 6}-8=...$$ commites.