Chapter 3 - Equations and Problem Solving - 3.2 - Equations and Problem Solving - Problem Set 3.2 - Page 106: 50

$\frac{A}{l}$ - $\frac{2\pi r^{2}}{l}$ = w

Using the properties of equality we obtain: $A = lw + 2\pi r^{2}$ Subtract both sides by 2$\pi$$r^{2}$ A - 2$\pi$$r^{2}$ = lw Divide both sides by l $\frac{A}{l}$ - $\frac{2\pi r^{2}}{l}$= w