Answer: The answer is 580
Step-by-step explanation: you first do the front side which is 20 x 10 which is 200. You multiply 200 by 2 since the front and back are the same.
then you move on to the sides.
the bottom of the side is 3. The height is 20. 3 x 20 is 60. Since there are 2 sides, you will do 60 x 2 which is 120.
now we move on too the top. The width of width is 3. and the length is 10. 10 x 3 is 30. Since the bottom is also the same, you do 30 x 2. You add all the numbers.
So 400 (from the front and back) + 120 (from the sides) + 60 ( from the top and bottom)
thiss all equals 580. sorry if it is a bit confusing I just understood it too. I am 14 trying to get math a year above me.