help with a math problem that i do not understand all the way

Question

A gallon of latex paint can cover 200 square feet. Maria has a rectangular room whose dimensions are 16 feet by 14 ​feet, with 8 ​-foot ceilings. How many gallon containers of paint does she need to buy to paint two coats on each​ wall?

Answer 1

each wall requires 16x14x8 = 1792

2 coats require 2 x 1792 = 3584

divide by 200 = 17.92 gallons of paint needed