Find the height of the aircraft if the atmospheric pressure is 197 millimeters of mercury
Unless you have been given an equation for atmospheric pressure vs. altitude, I don't see why this is considered an algebra question.
You can find the answer using the table in this web site:
http://www.engineeringtoolbox.com/air-altitude-pressure-d_462.html
The answer (interpolating in the table provided) is about 33,000 feet.