They are: 21, 42 and 63
21, 42 and 63
If that's 9, 14 and 21, the first three common multiples are 126, 252 and 378.
LCM of 21 & 49 is 147, so all multiples of 147 are common multiples of 21 & 49.
105 and 210
21
there are infinite amount of common multiples.
7, 14, 21
63, 126, 189
42, 84, 126
63, 126, 189
84, 168, 252