At what altitude does the plane fly if atmospheric pressure = 750 mm Hg near the Earth’s surface, and 450 mm Hg overboard?

We accept the value of the change in atmospheric pressure by 1 mm Hg. with an increase in height of 10 meters.
We find the difference in pressure at the surface of the earth and at the height.
750 – 450 = 300 mm Hg
We find the flight altitude of the aircraft.
300 * 10 = 3000 meters.
Answer: at an altitude of 3000 meters