Manometer problems deal in calculating the difference in gaseous pressure between any two surroundings. Normally, one outlet of the manometer is connected to a container filled with a certain gas, while the other outlet is left open to respond to room pressure. The mercury inside the manometer is displaced and the readings correspond to the pressure inside the container.
Manometer problems in high school physics usually involve a U-tube or Boyle's manometer filled with mercury at room temperature and pressure. When both outlets of the tube are in normal conditions, the mercury is at the same level in both arms of the U. Any change in pressure on either outlet of the manometer displaces the mercury and the height readings on the tube change.
Manometer problems are solved by simply calculating the difference in height in both arms of the tube. The difference is then added to the standard room pressure of 650 millimeters of mercury. For instance if the difference between the pressure inside a container of neon and room pressure is 10 millimeters on the tube, then the pressure inside the container of neon would be 650 - 10 = 640 millimeters of mercury. If the room-pressure arm of the tube shows a higher level of mercury, then the value 10 millimeters would be added to 650, hence resulting in 660 millimeters of mercury pressure inside the container.