1) Given this equation for Pressure, we need to plug into p the pressure of 318 lbs/ft² to get the depth according to the model described by this equation.
2) So, we can write out:
[tex]\begin{gathered} P=14+\frac{4d}{11} \\ 318=14+\frac{4d}{11} \\ 11\times318=11\times(14+\frac{4d}{11}) \\ 3498=154+4d \\ 3498-154=4d \\ 3344=4d \\ 4d=3344 \\ \frac{4d}{4}=\frac{3344}{4} \\ d=836ft \end{gathered}[/tex]Note that we multiplied both sides by 11 to get rid of the fraction.
Thus this is the depth below the surface that generates such pressure