Problem deals with change in pressure when temp is increased, use the relation
P1/T1 = P2/T2. P1 and T1 are initial pressure and temperature in Kelvin and P2and T2 are final pressure and temperature in Kelvin. To change to Kelvin add 273 to Celsius temp.
.55atm/173K = P2/473K
P2. = 1.5atm.