Confused about math prob?

Question

At the surface of the ocean, the water pressure is the same as the air pressure above the water, 15 lb/in^2. Below the surface, the water pressure increases 4.34 lb/in^2 for every 10ft of descent. (A) Express the water pressure as a function of the depth below the surface.

Answer 1

P (x) = 15 lb/in^2 + 0.434 lb/ft-in^2 * (x)  where x is the distance below the surface in ft (expressed as a positive number)