Write an equation or inequality to represent "five times the difference of a number n and forty two is ten more than twice the product of a number x and number y."

Sara goes on a slingshot ride in an amusement park. she is strapped into a spherical ball that has a radius 3*10^2 of centimeters. what is the volume of air in the spherical ball? use this formula: volume of a sphere=4/3pi, r^3 , where r is the sphere’s radius.