12. PLAYING WITH NUMBERS
Explanation:
36, 54,72
Multiples of 18 = 18, 36, 54...
Multiples of 6 = 6, 12, 18, ...
The first common multiple will be 18
And the next common multiples will be multiples of 18
Hence, first three common multiples of 18, 6 are 18, 36, 54