Answer:
The total number of days that Karen and Andy can use the beach house for personal use = 200 rental days x 10% = 20 days. If they exceed this limit, then they will not be able to deduct any rental losses from their income.
It is important to determine if Karen And Andy expect a rental loss or not. If they expect to lose money, then they should tell their daughter to use the beach house only for 6 days, not 7. Or they could use it only 13 days during the rest of the year. The important issue is that the total number of days for personal use doesn't exceed 10% of the rental days.