1. **State the problem:** Find the greatest common factor (GCF) of each given set of numbers. 2. **Recall the definition:** The GCF of a set of numbers is the largest positive integer that divides all the numbers in the set without leaving a remainder. 3. **Find the GCF for each set:** - For 8 and 12: - Factors of 8: 1, 2, 4, 8 - Factors of 12: 1, 2, 3, 4, 6, 12 - Common factors: 1, 2, 4 - Greatest common factor: $4$ - For 6, 7, and 21: - Factors of 6: 1, 2, 3, 6 - Factors of 7: 1, 7 - Factors of 21: 1, 3, 7, 21 - Common factors: 1 - Greatest common factor: $1$ - For 9 and 33: - Factors of 9: 1, 3, 9 - Factors of 33: 1, 3, 11, 33 - Common factors: 1, 3 - Greatest common factor: $3$ - For 9, 14, and 72: - Factors of 9: 1, 3, 9 - Factors of 14: 1, 2, 7, 14 - Factors of 72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36, 72 - Common factors: 1 - Greatest common factor: $1$ 4. **Summary:** - GCF(8, 12) = $4$ - GCF(6, 7, 21) = $1$ - GCF(9, 33) = $3$ - GCF(9, 14, 72) = $1$ The vertical line graph with points labeled from 0 to 4 likely represents a number line or scale but does not affect the GCF calculations here.