A rigid container has an initial pressure of 1.50 atm at 21oC. What will the pressure be if the temperature is increased to 121oC?

Answer 1

PV=kT
since V is constant, P/T is constant
so, you want P such that
P/(273+121) = 1.50/(273+21)

Answer 2

Or if you like to plug into a formula, it is
(P1/T1) = (P2/T2) and remember that T must be in kelvin which is
K = 273 + C