4.
Express each number in its prime composition in power form and take the lowest power of each prime across all the numbers (if a prime does not appear in any number, it does not appear in the gcf):
68 = 22 x 17
24 = 23 x 3
12 = 22 x 3
gcf = 22 = 4
The GCF is 4.
The GCF is 4.
The GCF is 4.
The GCF is 4.
The GCF of 24 and 12 is 12.
The greatest common factor of 24 and 68 is 4.4 x 6 = 244 x 17 = 68
The GCF is 4.
The GCF is 12.
The GCF is... 12
The GCF is 4.
The GCF of 20, 24, and 68 is 4.
The GCF is: 12