If the atmospheric pressure on mt. everest is one-third the atmospheric pressure at sea level, the partial pressure of oxygen on everest is

For simplicity, we assume ideal gas behavior. The oxygen content in the atmosphere at sea level is 21% in volume. Since it is assumed to be ideal gas, its partial pressure is 0.21 atm. One-third of this, which is 0.07 atm, is the oxygen's partial pressure on top of Mt. Everest.