We know that volume is : Base area times height .
here base is a rectangle : the length and width are : ( x+8) and ( x-3)
Area of the rectangle = length times width
= ( x+8)* ( x-3)
The volume o f the prism = base area times height
= ( x+8)( x-3) * (x-2)
Let us expand it . = ( x * x -3x + 8x - 8* 3 ) ( x-2)
= ( x^2 + 5x - 24)( x-2)
= x^2* x - 2x^2 + 5x* x - 5x* 2 - 24x -24*-2
= x^3 - 2x^2 + 5x^2 -10x -24x + 48
= x^3 + 3x^2 - 34x + 48
This is the expression for volume .