1. **State the problem:** We need to find the unit price per pen when a pack of 6 pens costs 4.50. 2. **Formula:** The unit price per pen is calculated by dividing the total cost by the number of pens. $$\text{Unit price} = \frac{\text{Total cost}}{\text{Number of pens}}$$ 3. **Substitute the values:** $$\text{Unit price} = \frac{4.50}{6}$$ 4. **Simplify the fraction:** $$\text{Unit price} = \frac{\cancel{4.50}}{\cancel{6}} = 0.75$$ 5. **Interpretation:** Each pen costs 0.75. **Final answer:** The unit price per pen is $0.75$.