I think I know how to do it
Your equation is:
P₁V₁ = P₂V₂
You Know:
Initial:
P₁ = 84 Pa
V₁ = 336 L
New:
P₂ = ?
V₂ = 216L
Plug this into the equation:
P₁V₁ = P₂V₂
(84 Pa)(336 L) = P₂(216 L) Divide 216 on both sides
[tex]\frac{(84Pa)(336L)}{216L}=\frac{(P_{2})(216L)}{216L}[/tex]
130.6666666 = P₂
(if your doing significant figures, you have 2 sig figs)
130 Pa = P₂