Verified answer

You need T in Kelvin to do these calculations

T1 = 323K and T2 = 373K

Then you just do (PV/T)initial = (PV/T)final

(20 kPa)(100L)/(323K) = (40 kPa)V/(373)

Rearranging to solve for V gives

V = (100 L)(20/40)(373/323)

57.74 L

PV=mRT

P1*V1/T1=P2*V2/T2

solve for V2

P1*V1*T2/P2T1=V2

I won't do the calculator for you...