First find the area of one of the long walls: 30 feet * 12 feet = <<30*12=360>>360 square feet
Then double that amount since there are two walls: 360 square feet * 2 = <<360*2=720>>720 square feet
Then find the area of the short wall: 20 feet * 12 feet = <<20*12=240>>240 square feet
Then add that area to the area of the two long walls to find the total area: 720 square feet + 240 square feet = <<720+240=960>>960 square feet
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