It's obvious that the reaction involved the gas to deplete (in volume).
Due to the depletion of the gas levels, we can conclude that the reaction "consumed" gas.
How much, we can calculate through a "conversion" formula:
The variables I literally rearranged this way for convienviency, it does not have to be in this order - you'll get the same answer (as long as you're consistent with the calculations
#H_"I"/P = H_"F"/P#
I cross-multiplied here
The final pressure of the gas is 507.28 torr.
Hope this helps :)