21

21

The GCF is the largest number that can divide a number

First get the prime factors of each number

42 = 2 *

the GCF = 3 * 7 = 21

First get the prime factors of each number

42 = 2 *

**3 * 7**63 = 3 ***3 * 7**the GCF = 3 * 7 = 21

3 is the gcf.