The first step is to subject the solid into two parts. We have
cuboid at the base and triangular prism at the top. Thus,
Volume = volume of cuboid + volume of triangular prism
The formula for calculating the volume of a cuboid is expressed as
V = length x width x height
From the diagram,
width = 9
height = 8
length = 12
Thus,
V = 12 x 9 x 8 = 864 cm^3
The formula for calculating the volume of a triangular base prism is expressed as
V = base area x height
base area = area of triangle = 1/2 x base x height
For the triangle,
base = 9
height = 15 - 8 = 7
Area of triangle = 1/2 x 9 x 7 = 31.5
Height of prism = 12
Volume of prism = 31.5 x 12 = 378 cm^2
Volume of shape = 864 + 378 = 1242 cm^3