This is a triangle prism, the base is a square and the four sides are equal triangles.
To find the surface area you need to first find the areas of the triangles, then the square, in the end you have to add them together.
Since we know the area of a triangle is 1/2bh we know that one if the triangle in the figure is
9*16/2=72(in^2)
there are four of these so we multiply it by 4
4*72=288(in^2 aka squared inches)
Then we need to find the area of the square. side * side=9*9=81 (in^2)
Add them together we get the surface area.
288+81=369 (in^2)
