The three are 84, 168, and 252 - the first three multiples of 84
(14 = 2 x 7, 84 = 2 x 2 x 3 x 7)
84 = 1 x 84 , 6 x 14
168 = 2 x 84, 12 x 14
252 = 3 x 84, 18 x 14
(only the sixth multiples of 14)
If that's 9, 14 and 21, the first three common multiples are 126, 252 and 378.
14, 28, 42.
14, 28, 42.
14, 28 and 42
14, 28, 42
42, 84, 126
42, 84, 126
14, 28, 42
7, 14, 21
14, 28, and 42
14, 28, 42
70, 140, 210 and so on.