Use the next law for a gas with constant volume:
[tex]\frac{P_1}{T_1}=\frac{P_2}{T_2}[/tex]Solve the equation above for T2 (new temperature):
[tex]\begin{gathered} T_2*\frac{P_1}{T_1}=P_2 \\ \\ T_2=P_2*\frac{T_1}{P_1} \end{gathered}[/tex]Use the given data to find the new temperature:
[tex]\begin{gathered} T_2=800torr*\frac{215K}{500torr} \\ \\ T_2=\frac{172000}{500}K \\ \\ T_2=344K \end{gathered}[/tex]