We have the following data:
[tex]\begin{gathered} n=3\text{ mol} \\ T=60\degree C=333.15K \\ V=5L \end{gathered}[/tex]In order to find the pressure (p) we apply the law of ideal gasses:
[tex]\begin{gathered} P\cdot V=n\cdot R\cdot T \\ R=0.082\frac{atm\cdot L}{\text{mol}\cdot K} \end{gathered}[/tex]Using the equation of ideal gasses we find that:
[tex]P=\frac{n\cdot R\cdot T}{V}=3\cdot\text{mol}\cdot0.082\frac{atm\cdot L}{\text{mol}\cdot K}\cdot333.15K\cdot\frac{1}{5L}=16.391\text{atm}[/tex]