The total pressure of the gas mixture is the summation of the partial pressure of all the gases in the container or Ptotal = P1 + P2 + P3 (have 3 gas species in mixture.
Please take notes on the following animated webpage of Dalton's Law of Partial Pressure.
[Click on play button to start animation]
Please take notes on the following animation of how to calculate (steps to follow) total pressure and/or partial pressure of gas mixtures.[Click on play button to start animation]
Thanks to www.chemistry.ohio-state.edu for animation webpages
Notes: