15 & 20 have an infinite number of Common Multiples; the first three are 60, 120 and 180.
First three common multiples of 15 and 20 would be: 60,120,180
10 and 15 15 and 20 20 and 25
60, 120 and 180
60 and all its multiples
The common multiples of 9, 15, and 20 are an infinite set of multiples of their least common multiple, which is 180. so the common multiples of 9, 15, and 20 are 180, 360, 540, 720, 900, 1080, 1260, 1440, 1620, 1800, and so on.
LCD= 60
60,120,180,240,300.... infinity
the first three common multiples of 7, 20, and 35 are 140, 280, and 420
10, 20, 30 The common multiples of 5 and 10 are multiples of their lowest common multiple. The lcm of 5 and 10, is 10. Thus the first three common multiples are 10, 20, 30.
The multiples of 20 are 20, 40, 60, 80, 100, 120... The multiples of 30 are 30, 60, 90, 120, 150... The multiples of 15 are 15, 30, 45, 60, 75, 90, 105, 120, 135... The common multiples of 20, 30, and 15 are 60, 120, 180, 240...
60 and 8,220
The LCM is 60