------------------------------------------------------------------ Find the width that is not planted with corn: ------------------------------------------------------------------ 15 - 5 = 10 feet
------------------------------------------------------------------ Find the Length that is not planted with corn: ------------------------------------------------------------------ 20 - 15 - 5 feet
------------------------------------------------------------------ Area that is not planted with corn: ------------------------------------------------------------------ 10 x 5 = 15 ft²
First you would add 27 and 9 to find the total number of games he sold, next you would divide 900 by 36 to get 25, then you would do 25 times 36 to check your answer.