Answer:
21
Explanation:
List the factors of 63 and 42:
- 63: 1, 3, 7, 9, 21, 63
- 42: 1, 2, 3, 6, 7, 14, 21, 42
Find the greatest factor listed in both lists:
- 21 in the greatest in both lists, so that is the answer (21 is the GCF of 63 and 42)
I hope this helps!