In this question, we have some gases in a container, and we can use Boyle's gas Law to solve this question, since what we have can be solved with only dealing with pressure and volume, the formula is:
P1V1 = P2V2
We have:
P1 = 1.0 atm
V1 = will be the sum of all the volumes, this is the initial volume of the gases, therefore it will be 4 + 6 + 10 = 20 L
P2 = ?
V2 = 8.0 L
Now we add these values into the formula:
1 * 20 = 8 * P2
P2 = 2.5 atm