Answer:
The greatest common factor (GCF) is the largest factor that divides two numbers and a factor is a number that divides into another number exactly so...
1)
10: 1,2,5,10
20: 1,2,4,5,10, 20
*10 is the GCF
2)
12: 1, 2, 3, 4, 6, 12
16: 1, 2, 4, 8, 16
*4 is the GCF
3)
27: 1, 3, 9, 27
36: 1, 2, 3, 4, 6, 9, 12, 18, 36
*9 is the GCF
