Can someone help me understand this?

The function p(d)=1+d/33 gives the pressure in the atmosphere (atm) at a depth in the sea (d is in feet) Note that P(0)=1 atm, P(33)=2 and so on find the pressure at 150 feet.
The pressure at 150 feet is ? atm?

evaluate P(150)

= 1 + 150/33
= 5.5454..