Least Common Multiple of 12, 15 and 18 by Listing Multiples

Multiples of 12: 12, 24, 36, 48, 60, 72, 84, 96, 108, 120, 132, 144, 156, 168, 180, 192, 204, …
Multiples of 15: 15, 30, 45, 60, 75, 90, 105, 120, 135, 150, 165, 180, 195, 210, …
Multiples of 18: 18, 36, 54, 72, 90, 108, 126, 144, 162, 180, …
LCM(12, 15, 18) = 180