Hello!
The least common multiple is the first multiple that both numbers have in common as shown below.
a.
6: 6, 12, 18, 24, 30
15: 15, 30
As you can see, the LCM is 30.
b.
4: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44
11: 11,22,33,44
c.
6: 6,12,18,24,30,36
9; 9,18,27,36
12: 12,24,36
d.
8: 8,16,24,32,40
10: 10, 20, 30, 40
20: 20,40
Therefore, our answers are below.
a. 30
b. 44
c. 36
d.40
I hope this helps!