Gas laws, finding pressure
We have PV=nRT
(where symbols have there usual meaning.)

You see V is constant as the container doesn't change or deform ( as you mentioned)

so thinking that way PV/nRT=constant
as moles are constant and not leaking
R is universal gas constant .
so ; 

P/T is constant 
then $P_1/ P_2 = T_1/T_2$