1. **State the problem:** Find the highest common factor (HCF) of 495 and 522. 2. **Recall the formula and rules:** The HCF of two numbers is the product of the prime factors common to both numbers, taken with the lowest powers. 3. **Prime factorization from the factor trees:** - For 495: $495 = 3 \times 3 \times 5 \times 11 = 3^2 \times 5 \times 11$ - For 522: $522 = 2 \times 3 \times 3 \times 29 = 2 \times 3^2 \times 29$ 4. **Identify common prime factors:** Both have $3^2$ in common. 5. **Calculate the HCF:** $$\text{HCF} = 3^2 = 9$$ 6. **Conclusion:** The highest common factor of 495 and 522 is 9.