1. **Problem:** The length of a rectangle is twice the width. The perimeter is 20 cm. Find the width. 2. **Formula:** The perimeter $P$ of a rectangle is given by $$P = 2(\text{length} + \text{width})$$ 3. **Step 1:** Let the width be $w$. Then the length is $2w$. 4. **Step 2:** Substitute into the perimeter formula: $$20 = 2(2w + w)$$ 5. **Step 3:** Simplify inside the parentheses: $$20 = 2(3w)$$ 6. **Step 4:** Multiply: $$20 = 6w$$ 7. **Step 5:** Solve for $w$ by dividing both sides by 6: $$\frac{20}{\cancel{6}} = \frac{6w}{\cancel{6}} \implies w = \frac{20}{6}$$ 8. **Step 6:** Simplify the fraction: $$w = \frac{10}{3} \approx 3.33 \text{ cm}$$ **Answer:** The width is $\frac{10}{3}$ cm or approximately 3.33 cm.