To find the area (not surface area because 'surface area' is measuring a 3D shape, whilst 'area' is measuring a 2D face.) of a triangle, you simply take your base and height, multiply by 2, then divide by 2 because a triangle is half of a parallelogram.
In this case, it's 11ft by 16ft. 16ft times 11ft = 176ft. Then 176ft divided by 2, which is 88.
Each triangular face has an area of 88ft.
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Now moving on to the square base, the dimensions are 11ft by 11ft. To find the area of a square, you multiply L(ength) times W(idth).
In this case, it's 121ft.
Now, you have 121ft as your square base, and 88ft each triangular face. The total surface area is 209ft.
Hope this helped.