what is the GCF of 12,20,26

12 is your smallest number so you know that it can be no larger than 12. It also must be included in 12's factors so I would start there.12's factors include 1,2,3,4,6, and 12. I would start just plugging them inone always works so but we could always use it as a backup20/2=10 so that works26/2=13 so if worst comes to worst we have 220/3=6.666 so that doesn't work20/4=526/4=6.5 so that doesn't work eitherBecause 3 doesn't work and 3 goes into 6 we know 6 doesn't work eitherThe same thing happens with 12 so 12 doesn't work either. Now we just go back and find the numbers that worked (1 and 2) Out of those numbers 2 is the largest so it is our greatest common factor.