Idon’t understand if you could explain that would be great for me

Think of the doghouse as being a rectangular prism bottom and a triangular prism on top.

volume of prism: area of the base * height

Rectangular prism:

The base is a square 4.5 ft by 4.5 ft.

The height is 3.0 ft.

volume = 4.5 ft * 4.5 ft * 3.0 ft = 60.75 ft^3

Triangular prism:

The triangle facing the front is the base. The height is the depth, 4.5 ft.

For the triangle, the area is bh/2, where b = 4.5 ft, h = 1.5 ft

volume = bh/2 * height

volume = 4.5 ft * 1.5 ft / 2 * 4.5 ft = 15.1875 ft^3

Total volume = 60.75 ft^3 + 15.1875 ft^3

Total volume = 75.9375 ft^3