Surface Area is the area of each face added together. For this question lets find the area of one triangle first.
Area of a triangle is base*hight/2, so 6*7/2=21. That was the area of one triangle. We have 4 traingle so we multiply that by for. 21*4=84.
Now, lets find the area of the squre. area of square is side*side or side^2.
So we multiply 6*6=36. that is the area of the square.
To find the surface area, we must add Area of Triangles+Area of Square.
so, 84+36=120
So the surface area is 120