Discuss PGroot's answer to: What set contains all prime numbers 9 12 27, 15 25 45, 16 25 36, 17 19 37, 24 48 72?

All prime means that none of the numbers can be factored.  You can easily eliminate the sets with an even number since they all have a factor of 2, and the ones that end in 5 all have a factor of 5.  If there were numbers like 21 39 91 you would have more work to factor them.

I'm not spelling out the answer but you can figure it out easily from those clues.