Question

What is the greatest common factor of 12 and 16?

Answer 1

$Greatest\ common\ factor\ is\ the\ highest\ number\ by\ witch\ 12\ and\ 16\\can\ be\ divided\\\\ 12:2\\ 6:2\\3:3\\\\ 16:2\\ 8:2\\4:2\\2:2\\\\GCF=2^2=4\\\\Greatest\ common\ factor\ of\ 12\ and\ 16\ is\ equal\ to\ 4.$

Answer 2

Split each number into prime factors:

12=2x2x3
16=2x2x2x2

Find the number that appears in both and find how the maximum number it reoccurs in both, in this case 2 reoccurs twice.
The GCF of 12 and 16 is 4.