1. **State the problem:** A duck flies 9 kilometers in 6 minutes. We want to find how far it can fly in 42 minutes. 2. **Set up the proportion:** Let $d$ be the distance the duck can fly in 42 minutes. Since the rate is constant, the ratio of distance to time is the same: $$\frac{d}{42} = \frac{9}{6}$$ 3. **Solve the proportion:** Cross-multiply to solve for $d$: $$6 \times d = 9 \times 42$$ $$6d = 378$$ 4. **Divide both sides by 6:** $$d = \frac{378}{6}$$ Show canceling common factors: $$d = \frac{\cancel{378}}{\cancel{6}} = 63$$ 5. **Final answer:** The duck can fly **63 kilometers** in 42 minutes.