Step 1
Given;
[tex]\begin{gathered} P_1=3atm \\ v_1=12l \\ v_2=6l \\ p_2=? \end{gathered}[/tex]Step 2
Boyle's law is given as
[tex]p_1(v_1)=p_1(v_2)[/tex][tex]\begin{gathered} 3(12)=6(p_2) \\ 36=6p_2 \\ p_2=\frac{36}{6}=6atm \end{gathered}[/tex]Answer;
[tex]The\text{ new pressure = 6atm}[/tex]