GCF stands for greatest common factor so if u have a problem like let's say, "What is the gcf of 36 and 90?" all u do is go down your multiples table and write them all down till 36 you will get 9 and if u take 10×9 it equals 90. For LCM all you do is go down your multiples table and find the least number that is the same with each other.