Paper he needs = total surface area
So to break it down into 2D shapes, that prism has 2 2D triangles, and 3 2D rectangles of different sizes.
The triangles are the same size, since you have 2, just multiply 2 by the formula for the area of a triangle: 1/2(base)(height) which is 2x1/2(5)(12) = 60
Next you'll need the area of all the rectangles: length x width. which would be (5 x 5) + (13 x 5) + (12 x 5) = 150
So the total amount of wrapping paper he'd need is 150mi^2
