Answer:
Sum of their partial pressures
Step-by-step explanation:
If two gases are present in a container, the total pressure in the container is equal to the sum of their partial pressures.
This solution is based on the Dalton's Law of Partial Pressures.
Dalton's Law of Partial Pressure states that "the total pressure of a mixture of gases is equal to the sum of the partial pressures of the constituent gases".
A partial pressure is the pressure a gas would exert if it alone occupied the volume of the gas mixture.