Answer
The organizer owes the winner $\frac{2}{5}$.
Work Step by Step
The organization paid the winner $\frac{3}{10}$ of her winnings. If the organization originally owed $\frac{7}{10}$ of her winnings, they now owe the difference between $\frac{7}{10}$ and $\frac{3}{10}$.
$\frac{7}{10}-\frac{3}{10}=\frac{7-3}{10}=\frac{4}{10}=\frac{4\div2}{10\div2}=\frac{2}{5}$
Therefore, they currently owe the winner $\frac{2}{5}$ of the original winnings.
