Answer:
252 square feet
Step-by-step explanation:
Surface area is the addition of the area of all of the faces in a object. There are 2 bases in a triangular prism and both are triangles to the formula is b*h/2. So you would do 3*4/2=6 and since there are 2 bases it is 12 sqaure feet for both of the bases. For the rectangular sides, they are rectangules so the formula would be b*h. You would find the area of each of the rectangular sides. So, 20*3=60 square feet, 20*4=80 square feet, and 20*5=100 square feet. After that you should add up all the areas so 12 square feet +60 square feet +80 square feet +100 square feet =252 square feet which is the suface area.
