1. **State the problem:** Find the unit rate of miles per gallon given 450 miles and 15 gallons. 2. **Formula:** The unit rate is found by dividing the total miles by the total gallons: $$\text{Unit rate} = \frac{\text{miles}}{\text{gallons}}$$ 3. **Divide the miles by gallons:** $$\frac{450}{15}$$ 4. **Simplify the division:** $$\frac{\cancel{450}}{\cancel{15}} = 30$$ 5. **Interpretation:** This means for every 1 gallon, the car travels 30 miles. 6. **Final answer:** The unit rate is **30 miles per 1 gallon** or simply **30 mi/gal**.