#### Answer

72

#### Work Step by Step

The LCM of a group of numbers is the smallest number into which the original numbers divide. Therefore, we can list the multiples of each number, and the number that first appears as a multiple of all of the numbers will be the LCM.
8- 8, 16, 24, 32, 40, 48, 56, 64, 72
9- 9, 18, 27, 36, 45, 54, 63, 72
12- 12, 24, 36, 48, 60, 72
18- 18, 36, 54, 72
Therefore, 72 is the LCM of 8,9, 12, and 18.