Answer:
4
Explanation:
The greatest common factor is the largest number that is a shared factor of all 3 numbers (the greatest number they can all divide into). To find the GCF, we can list all the factors of the 3 numbers and then find the largest one that is common to all three sets.
Factors of 12 are: 1,2,3,4,6,12
Factors of 16 are: 1,2,4,8,16
Factors of 20 are: 1,2,4,5,10,20
We can see that 1,2 and 4 are the numbers common to all three sets but 4 is the largest so 4 is our greatest common factor.
Hope this helped!