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

$\displaystyle {P}={13}+\frac{{{6}{d}}}{{13}}$

If a scientific team uses special equipment to measures the pressure under water and finds it to be 115 pounds per square foot, at what depth is the team making their measurements?

Answer: The team is are measuring at feet below the surface.