Least Common Multiple of 6, 7 and 12 by Listing Multiples

Multiples of 6: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78, 84, 90, 96, …
Multiples of 7: 7, 14, 21, 28, 35, 42, 49, 56, 63, 70, 77, 84, 91, 98, …
Multiples of 12: 12, 24, 36, 48, 60, 72, 84, …
LCM(6, 7, 12) = 84