Answer:
C
Explanation:
what is the greatest common factor of 72 and 54 ?
in other words, what is the biggest number that divides both numbers without remainder ?
I use a prime factor analysis (identify all the prime factors).
72 :
72 ÷ 2 = 36
36 ÷ 2 = 18
18 ÷ 2 = 9
9 ÷ 2 no
9 ÷ 3 = 3
3 ÷ 3 = 1 finished
72 = 2⁴×3²
54 :
54 ÷ 2 = 27
27 ÷ 2 no
27 ÷ 3 = 9
9 ÷ 3 = 3
3 ÷ 3 = 1 finished
54 = 2×3³
the largest number that can divide them both without remainder is the combination of the prime factors they have in common :
2 × 3² = 18