Chapter 5 Polynomials and Polynomial Functions - 5.4 Factor and Solve Polynomial Equations - 5.4 Exercises - Problem Solving - Page 359: 65b

See below.

For all 3 solids, the volume is the product of their height, width and length. Thus for Solid I: $a\cdot a\cdot(a-b)=a^2(a-b)$. for Solid II: $a\cdot b\cdot(a-b)=ab(a-b)$. for Solid III: $b\cdot b\cdot(a-b)=b^2(a-b)$.