Gerald can put 6 blue mints and 7 red mints in each bag. The greatest number of mints IN ALL he can put in his bag is 13 to have no more left remaining. (6+7=13)
If you find the greatest common factor for both 36 and 42, it would be 6. You’d divide 36 by 6 to get 6. While 42 divided by 6 is 7.