$PV ^{\gamma}=$ constant
$V _{2}=\frac{ V _{1}}{8}$
$P _{1} V _{1}^{\gamma}= P _{2} V _{2}^{\gamma}$
$P _{1} V _{1}^{\gamma}= P _{2}\left(\frac{ V _{1}}{8}\right)^{5 / 3}$
$P _{1} V _{1}^{5 / 3}=\frac{ P _{2} V _{1}^{5 / 3}}{32}$
$P _{2}=32 P _{1}$


(Take $R$ = $8.3\ J/mol-K$ and $ln\ 2$ = $0.69$)
