How find the greatest common factor for 96 and 51?

The factors of 51 are:

1, 3, 17, 51

The factors of 96 are:

1, 2, 3, 4, 6, 8, 12, 16, 24, 32, 48, 96

The common factors are:

1, 3

The Greatest Common Factor:

GCF = 3

Prime factorisations:

96 = 25*3

51 = 3*17

Common factors = 3 so GCF = 3.