25(1.15)^6 is the formula for that problem because the 6 acts as the multiplier for how many weeks, while the 1.15 stands as the increase over those six weeks
In this problem the surface area of the composite figure is equal to the area of the base of the rectangular prism plus the lateral area of the rectangular prism, plus the area of the two triangular faces of triangular prism, plus the area of two rectangular faces of the triangular prism. we know that