This question is based on the ideal gas law [tex]PV=nRT[/tex], where [tex]P[/tex] is the pressure, [tex]V[/tex] is the volume,[tex]n[/tex] is number of moles,[tex]R[/tex] is the gas constant which can take many values depending on the units. In this problem we will use [tex]0.082057Latmmol^-^1K^-^1[/tex] to get our pressure in atm. So we male P the subject of the formula
[tex]P=\frac{nRT}{V}= \frac{(0.703*0.08205*314)}{15}=\frac{18.11}{15}= 1.2atm[/tex]