Finding surface area if an triangular prism

1)find the area of a triangle. Multiply it by 2 or 4 depending on if they are the same size
2)find the area of the base
3)find the area of the other two sides if you haven’t already.
4) add them all together

Best answer that i found on yahoo ok   set :   x= length of 2nd piece in cm  x- 3= length of 1st piece in cm  x-4= length of 3rd piece in cm  then since you know they all came from the 20 cm ribbon you add them together and set them equal to 20x+ x-3 +x-4 = 20  3x - 7= 20  3x= 27  x= 9  the shortest piece is the third piece which is x- 4  x-4  9-4 = 5  the length of the smallest piece is 5 cm.  the other lengths are  9 cm  6 cm