They are members of an infinite set of numbers of the form 42*k where k is an integer.
7, 14, 21, 28, 35, 42, 49, 56, 63, 70, etc.
12
3, 6, 9, 12, 15 and so on.
60, 120, 180 and so on.
4, 8, 12, 16, 20, 24 and so on.
The GCF of 42 and 84 is 42.
42/2, 42/3, 42/4, 42/5, 42/6, 42/7, 42/8 and 42/9.
LCM(14, 42) = 42
7x6=42
42 + 42 = 84
42
6X7=42 BECAUSE YOU HAVE 6 GROUPS OF 7 SO THAT MAKES IT 42