the GCF of 12 and 30
6 is the greatest common factor of 12 and 30
so ur doing GCF- greatest common factor the buggest number that both numbers have in common... 12- 1,2,3,6,12 30 -1,2,3,5,6,1015,39 ...so as you see 6 is the greatest common factor of 12 and 30