Answer: 8
Step-by-step explanation: Solve this problem with GCF (Greatest Common Factor).
Factors of 56: 1, 2, 4, 7, 8, 14, 28 and 56.
Factors of 72: 1, 2, 3, 4, 6, 8, 9, 12, 18, 24, 36 and 72.
So, the biggest among the numbers that are matching is 8.