We have two expressions: 4a + 16 and 6a + 24
Both terms have a even coefficient, then they must have a common factor 2:
2(2a + 8) and 2(3a + 12)
Now we can check that (2a + 8) and (3a + 12) don't have common factors
The least common multiple must be composed by all the major factors of both expressions. Then, the least common multiple of (4a + 16) and (6a + 24) must be given by:
2*(2a + 8)*(3a + 12) = 12a² + 96a + 192