This is a method I found that gives you greatest common factor and lowest common multiple. First you get two numbers you need to find GCF and or LCM for. (140 and 180) then you must find a common factor for both. (10) then divide both numbers by the common factor (140 turns into 14 and 180 turns into 18) repeat until you have prime factors. To find the GCF you multiply only the numbers on the side. (GCF: 10×2=20 GCF=20) to find LCM you must multiply all of the numbers beside the L shape on the outside. (LCM: 10x2x7x9=1260 LCM=1260)