1. **State the problem:** Find the highest common factor (HCF) of 8, 12, and 20 using their factor trees. 2. **Write the prime factorization from the factor trees:** - For 8: $$8 = 2 \times 4 = 2 \times 2 \times 2 = 2^3$$ - For 12: $$12 = 3 \times 4 = 3 \times 2 \times 2 = 2^2 \times 3$$ - For 20: $$20 = 5 \times 4 = 5 \times 2 \times 2 = 2^2 \times 5$$ 3. **Identify common prime factors:** - The prime factors common to all three numbers are the 2's. 4. **Find the lowest power of common primes:** - For 2, the powers are 3 (in 8), 2 (in 12), and 2 (in 20). - The lowest power is 2. 5. **Calculate the HCF:** $$\text{HCF} = 2^2 = 4$$ 6. **Final answer:** The highest common factor of 8, 12, and 20 is **4**.