An underwater air bubble has an excess inside pressure of 13 pa. what is the excess pressure inside an air bubble with twice the radius?

Pressure = 2 * pi * sigma * radius where sigma is the pressure constant of the medium or the material.

Thus, Pressure/Radius = constant

Based on this:

(pressure*radius) in case 1 = (pressure*radius) in case 2

(13 * R) = (P * 2R)

P = 13/2 = 6.5 pa