Answer:
1. 20, 10, 5, 4, 2
2. 20
2nd page
Common factors of 12,48
2,3,4,6,12
GCF:12
Common factors of 12,72
2,3,4,,6,12
GCF:12
Common factors of 72,48
2,3,4,6,8,12,24
GCF:24
Common factors of 12,48,72
2,4,6,12
GCF:12
Last page is
D I think I am not sure
