Not sure if I understand the following but I believe the solution is wrong? Shouldnt be 35, 66, 121?
11 is common to both 66 and 121 so they cannot be co-prime.
The question is using coprime to mean pairwise coprime: every pair must have GCD 1.
Since 66 and 121 have a common factor of eleven, 35, 66, 121 are not pairwise coprime.
Perhaps, specifying that will help. @Leaderboard
Where is this question from?
Edit: fixed it.