What is the central or main idea? how do you find the central or main idea of a text?

this is the answer , p = 1 + (1/10)x

step-by-step explanation:

we have,

at sea level pressure is 1 atmosphere (i.e at x =0, p0=1 atmosphere)

at depth 23 meters , pressure = 3.3 atmosphere

since the pressure increases at constant rate as the depth increases, so we can write a relation as:

p =p0 +   kx   , where p is the pressure  , p0 is the initial pressure, x is the depth and k is constant rate of increasing.

to find constant rate k, plug p = 3.3 , p0 = 1 and x= 23 meters

we get,

  3.3 = 1 + k * 23

k = 2.3 / 23   = 1/10

so we can write the function formula as:   p = 1 + (1/10)x