1) if its cross-section is a trapiezium, calculate the maximum volume of waste material it can hold when filled up level to its brim.
do u work out area of trapezium first?
1/2 * sum of parallel sides * height
0.5 * 13 * 5 = 32.5cm squared?
how u work out the volume?
2) how do i calculate the volume of this shape?
it's the same method as I've shown in #1). So turn the solid until the triangle is the base area. Then you have a prism. The only problem here is, that you can't calculate the area of the triangle because it is not determined. (You need an angle or the length of the 3rd side of the triangle to calculate properly first the area and afterwards the volume)