In certain deep parts of oceans, the pressure of sea water, P, in pounds per square foot, at a depth of d feet below the surface, is given by the following equation:

P = 16+4d/9

If a scientific team uses special equipment to measures the pressure under water and finds it to be 172 pounds per square foot, at what depth is the team
making their measurements?
Answer: The team is measuring at ???? feet below the surface.