James is building a hall of mirrors. Three of the walls will be completed covered with glass. If two of those walls are 30 feet by 12 feet and the third is 20 feet by 12 feet, how many square feet of glass does he need?
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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