What is the partial pressure of helium gas in a sealed vessel that has a total pressure of 205 kPa and partial pressures of 15 kPa for chlorine and 89 kPa for fluorine?
The total pressure is the sum of the partial pressures.
Dalton's law of partial pressures states that in a gaseous mixture, the partial pressure of a gaseous component is the same as the pressure that gas would exert if it ALONE occupied the container.......
The total pressure is the sum of the individual partial pressures.
In your problem, which you described well,