Area of the triangle = (1/2)*base* height = (1/2)*3*6 = 9 sm²
We have 4 triangles like this one ,
so area of 4 triangles = 9*4 = 36 cm².
Area of the square = 3*3 = 9 cm²
Surface area here means area all triangles + area of the square =36 +9 =
= 45 cm ²
Answer is 45 cm².