We can approach this problem using the ideal gas law which is as follows:
PV = nRT
P = pressure
V = volume
n = number of moles
R = gas constant, 0.08206 Latm/Kmol
T = temperature
We are asked to solve for temperature and can rearrange the equation to solve for T:
PV = nRT
T = PV/nR
Now we simply plug in the data to solve for T:
T = (4.50 atm)(10.0 L)/(3.00 mol)(0.08206 Latm/Kmol)
T = 183 K
The temperature of the gas is 183 K.