What we're going to do is to use the following:
Remember! Temperature must always be in Kelvin.
What we're going to do is to check the values that we know: (To pass from Celcius to Kelvin, what we do is to add 273.15)
V1 = 81.1 L
T1 = 31.5 °C = 304.65 K
P1 = 491.7 mmHg
V2 = 204 L
T2 = 6.9°C = 280.05 K
P2 = ?
What we're going to do is to replace all these values in the equation and then solve for P2:
Therefore, the correct answer is about 180 mmHg.