1. **State the problem:** We need to find the missing width $w$ of a rectangular prism given its volume and two other dimensions. 2. **Given:** - Volume $V = 220.5$ cm³ - Height $h = 7$ cm - Length $l = 7$ cm - Width $w = ?$ cm 3. **Formula:** The volume of a rectangular prism is given by $$V = l \times w \times h$$ 4. **Substitute known values:** $$220.5 = 7 \times w \times 7$$ 5. **Simplify the right side:** $$220.5 = 49 \times w$$ 6. **Solve for $w$ by dividing both sides by 49:** $$w = \frac{220.5}{49}$$ 7. **Show cancellation:** $$w = \frac{\cancel{220.5}}{\cancel{49}}$$ 8. **Calculate the division:** $$w = 4.5$$ 9. **Answer:** The missing width $w$ is 4.5 cm.