Convert all the pressures into one unit and then, using Dalton's
Law of Partial Pressure, you just add all the pressures
together.
Using these conversions(101325Pa equals 1 ATM, 1 ATM equals 760
mmHg, 1 mmHg equals 1 torr), calculate each pressure into one
unit(I used mmHg)
1013000 Pa nitrogen equals 7598 mmHg of nitrogen(make sure you
round using sig figs)
700 mmHg of argon equals 700 mmHg of argon
1.20 ATM of helium equals 912 mmHg of helium
790 torr oxygen equals 790 mmHg of oxygen
0.50 ATM of carbon dioxide equals 380 mmHg of Carbon Dioxide
Now add all the pressures and you get:
7598+700+912+790+380= 10380 mmHg
If you need to have the answer in a particular unit:
10380 mmHg
= 10380 torr
= 13.66 ATM
= 1384000 Pa
= 1,384 kPa