Answer: 54x^2+360x+600
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Step-by-step explanation:
One square face has an area of
(length)*(width) = (3x+10)(3x+10) = 9x^2+30x+30x+100 = 9x^2+60x+100
after using the FOIL rule
Multiply that by 6 to get the total area of all 6 faces
6*(9x^2+60x+100) = 54x^2+360x+600
The surface area units are in square feet.