Answer: The volume of balloon at higher altitude is 631.3 L
Step-by-step explanation:
To calculate the volume when temperature and pressure has changed, we use the equation given by combined gas law. The equation follows:

where,
 are the initial pressure, volume and temperature of the gas
 are the initial pressure, volume and temperature of the gas
 are the final pressure, volume and temperature of the gas
 are the final pressure, volume and temperature of the gas
We are given:
Conversion factor: 1 atm = 760 mmHg
![P_1=759mmHg=0.99atm\\V_1=50.0L\\T_1=22.3^oC=[273+22.3]K=295.3K\\P_2=0.0701atm\\V_2=?L\\T_2=-9.00^oC=[273-9]=264K](https://img.qammunity.org/2020/formulas/chemistry/college/hk82qh3oawmnl14io3xyvzp5hnhf4vynit.png)
Putting values in above equation, we get:

Hence, the volume of balloon at higher altitude is 631.3 L