$$ Wins = 8,\ \ \ Losses=5, \ \ \ Ties=0 $$

$$ Total\ games\ played = 13 $$

$$ Games\ remaining=10 $$

$$ Total\ games\ =\ 23 $$

$$ 50\%\ of\ 23=11.5 $$

As 12 is greater than 50% of 23 and girls have played 8 games so they have to win 4 more games