I'm only answering because the app told me i need to help someone before I can ask another question, but I can't help because I don't know what to help you with so
The sum is the gcf, if 60 plus 84 is 148 then wouldn't it be 148 that's what they all have in common, you can use a calculator to figure this out like say 148 times 2 equals 296, divide 296 by 60. Does it go in?
