Answer:
10 atm
Step-by-step explanation:
Assuming the gas is kept at constant temperature, we can apply the following law (Boyle's law):
"For a gas kept at a constant temperature, the pressure of the gas is inversely proportional to its volume"
Mathematically,

where p is the pressure of the gas and V its volume.
The equation can also be rewritten as

Where for the gas in the problem, we have:
is the initial pressure
is the initial volume
is the final pressure
is the final volume
Solving for p2,
